Статті в журналах: "Weak Scale Supersymmetry"

1

Hall, L. J., and L. Randall. "Weak-scale effective supersymmetry." Physical Review Letters 65, no. 24 (December 10, 1990): 2939–42. http://dx.doi.org/10.1103/physrevlett.65.2939.

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2

Anderson, Greg W., and Diego J. Castaño. "Challenging weak-scale supersymmetry at colliders." Physical Review D 53, no. 5 (March 1, 1996): 2403–10. http://dx.doi.org/10.1103/physrevd.53.2403.

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3

Erler, Jens. "Chiral models of weak scale supersymmetry." Nuclear Physics B 586, no. 1-2 (October 2000): 73–91. http://dx.doi.org/10.1016/s0550-3213(00)00427-2.

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4

Kribs, Graham D. "Supersymmetric Lepton Flavor Violation, the Muon Anomalous Magnetic Moment, and e- e- Colliders." International Journal of Modern Physics A 18, no. 16 (June 30, 2003): 2769–78. http://dx.doi.org/10.1142/s0217751x03016239.

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I explain the theoretical connection between lepton flavor violation and muon g - 2 in supersymmetry1. Given any central value deviation of muon g - 2 from the standard model that is assumed to be due to weak scale supersymmetry, I show that stringent bounds on lepton flavor violating scalar masses can be extracted. These bounds are essentially independent of supersymmetric parameter space. I then briefly compare this indirect handle on supersymmetric lepton flavor violation with direct observation at a future lepton collider operating in the e- e- mode. This is a summary of a talk given at e- e-01: 4th International Workshop on Electron-Electron Interactions at TeV Energies.

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5

Allanach, Ben C. "Multiple solutions in supersymmetry and the Higgs." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2032 (January 13, 2015): 20140035. http://dx.doi.org/10.1098/rsta.2014.0035.

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Weak-scale supersymmetry is a well-motivated, if speculative, theory beyond the Standard Model of particle physics. It solves the thorny issue of the Higgs mass, namely: how can it be stable to quantum corrections, when they are expected to be 10 15 times bigger than its mass? The experimental signal of the theory is the production and measurement of supersymmetric particles in the Large Hadron Collider (LHC) experiments. No such particles have been seen to date, but hopes are high for the impending run in 2015. Searches for supersymmetric particles can be difficult to interpret. Here, we shall discuss the fact that, even given a well-defined model of supersymmetry breaking with few parameters, there can be multiple solutions. These multiple solutions are physically different and could potentially mean that points in parameter space have been ruled out by interpretations of LHC data when they should not have been. We shall review the multiple solutions and illustrate their existence in a universal model of supersymmetry breaking.

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6

NATH, PRAN. "HIGGS PHYSICS AND SUPERSYMMETRY." International Journal of Modern Physics A 27, no. 28 (November 10, 2012): 1230029. http://dx.doi.org/10.1142/s0217751x12300293.

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A brief overview of Higgs physics and of supersymmetry is given. The central theme of the overview is to explore the implications of the recent discovery of a Higgs-like particle regarding the prospects for the discovery of supersymmetry assuming that it is indeed the spin-0 CP even boson that enters in the spontaneous breaking of the electroweak symmetry. The high mass of the Higgs-like boson at ~125 GeV points to the weak scale of supersymmetry that enters in the loop correction to the Higgs boson mass, to be relatively high, i.e. in the TeV region. However, since more than one independent mass scales enter in softly broken supersymmetry, the allowed parameter space of supersymmetric models can allow a small Higgs mixing parameter μ and light gaugino masses consistent with a ~125 GeV Higgs boson mass. Additionally some light third generation sfermions, i.e. the stop and the stau are also permissible. Profile likelihood analysis of a class of SUGRA models indicates that mA>300 GeV which implies one is in the decoupling phase and the Higgs couplings are close to the standard model in this limit. Thus a sensitive measurement of the Higgs couplings with fermions and with the vector bosons is needed to detect beyond the standard model effects. Other topics discussed include dark matter, proton stability, and the Stueckelberg extended models as probes of new physics. A brief discussion of the way forward in the post Higgs discovery era is given.

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7

Bagger, Jonathan A., Konstantin T. Matchev, Damien M. Pierce, and Ren-Jie Zhang. "Weak-scale phenomenology of models with gauge-mediated supersymmetry breaking." Physical Review D 55, no. 5 (March 1, 1997): 3188–200. http://dx.doi.org/10.1103/physrevd.55.3188.

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8

Köhler, Nicolas. "Searches for direct pair production of third generation squarks with the ATLAS detector." EPJ Web of Conferences 182 (2018): 02065. http://dx.doi.org/10.1051/epjconf/201818202065.

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Naturalness arguments for weak-scale supersymmetry favour supersymmetric partners of the third generation quarks with masses not too far from those of their Standard Model counterparts. Top or bottom squarks with masses less than or around one TeV can also give rise to direct pair production rates at the Large Hadron Collider (LHC) that can be observed in the data sample recorded by the ATLAS detector. This document presents recent ATLAS results from searches for direct top and bottom squark pair production considering both R-parity conserving and R-parity violating scenarios, using the data collected during the LHC Run 2 at a centre-of-mass energy of √s = 13 TeV.

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9

Baer, Howard, Vernon Barger, Dibyashree Sengupta, Shadman Salam, and Kuver Sinha. "Status of weak scale supersymmetry after LHC Run 2 and ton-scale noble liquid WIMP searches." European Physical Journal Special Topics 229, no. 21 (December 2020): 3085–141. http://dx.doi.org/10.1140/epjst/e2020-000020-x.

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10

Anderson, Greg W., and Diego J. Castaño. "Naturalness and superpartner masses or when to give up on weak scale supersymmetry." Physical Review D 52, no. 3 (August 1, 1995): 1693–700. http://dx.doi.org/10.1103/physrevd.52.1693.

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11

Nath, Pran. "High energy physics and cosmology at the unification frontier: Opportunities and challenges in the coming years." International Journal of Modern Physics A 33, no. 20 (July 20, 2018): 1830017. http://dx.doi.org/10.1142/s0217751x1830017x.

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We give here an overview of recent developments in high energy physics and cosmology and their interconnections that relate to unification, and discuss prospects for the future. Thus there are currently three empirical data that point to supersymmetry as an underlying symmetry of particle physics: the unification of gauge couplings within supersymmetry, the fact that nature respects the supersymmetry prediction that the Higgs boson mass lie below 130 GeV, and vacuum stability up to the Planck scale with a Higgs boson mass at [Formula: see text][Formula: see text]125 GeV while the Standard Model does not do that. Coupled with the fact that supersymmetry solves the big hierarchy problem related to the quadratic divergence to the Higgs boson mass square along with the fact that there is no alternative paradigm that allows us to extrapolate physics from the electroweak scale to the grand unification scale consistent with experiment, supersymmetry remains a compelling framework for new physics beyond the Standard Model. The large loop correction to the Higgs boson mass in supersymmetry to lift the tree mass to the experimentally observable value, indicates a larger value of the scale of weak scale supersymmetry, making the observation of sparticles more challenging but still within reach at the LHC for the lightest ones. Recent analyses show that a high energy LHC (HE-LHC) operating at 27 TeV running at its optimal luminosity of [Formula: see text] can reduce the discovery period by several years relative to HL-LHC and significantly extend the reach in parameter space of models. In the coming years several experiments related to neutrino physics, searches for supersymmetry, on dark matter and dark energy will have direct impact on the unification frontier. Thus the discovery of sparticles will establish supersymmetry as a fundamental symmetry of nature and also lend direct support for strings. Further, discovery of sparticles associated with missing energy will constitute discovery of dark matter with LSP being the dark matter. On the cosmology front more accurate measurement of the equation of state, i.e. [Formula: see text], will shed light on the nature of dark energy. Specifically, [Formula: see text] will likely indicate the existence of a dynamical field, possibly quintessence, responsible for dark energy and [Formula: see text] would indicate an entirely new sector of physics. Further, more precise measurements of the ratio [Formula: see text] of tensor to scalar power spectrum, of the scalar and tensor spectral indices [Formula: see text] and [Formula: see text] and of non-Gaussianity will hopefully allow us to realize a Standard Model of inflation. These results will be a guide to further model building that incorporates unification of particle physics and cosmology.

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12

Meloni, Federico. "Searches for Direct Pair Production of Third Generation Squarks with the ATLAS Detector." International Journal of Modern Physics: Conference Series 46 (January 2018): 1860057. http://dx.doi.org/10.1142/s2010194518600571.

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This document summarises recent ATLAS results for searches for third generation squarks using 36.1 [Formula: see text] of LHC proton-proton collision data collected at [Formula: see text] TeV. Despite the absence of experimental evidence, weak scale supersymmetry remains one of the best motivated and studied Standard Model extensions. Supersymmetry can naturally solve the Standard Model hierarchy problem by preventing a large fine-tuning in the Higgs sector: a typical natural SUSY spectrum contains light third generation squarks (stops and sbottoms). Both R-Parity conserving and R-Parity violating scenarios are considered. The searches involve final states including jets, missing transverse momentum, electrons or muons. Simplified models predicting pair production of third generation squarks have been excluded at 95% CL up to about one TeV in the most favourable scenarios.

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13

SUEMATSU, DAIJIRO, and YOSHIO YAMAGISHI. "RADIATIVE SYMMETRY BREAKING IN A SUPERSYMMETRIC MODEL WITH AN EXTRA U(1)." International Journal of Modern Physics A 10, no. 31 (December 20, 1995): 4521–36. http://dx.doi.org/10.1142/s0217751x95002096.

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Radiative symmetry breaking is studied in a superstring-inspired supersymmetric model which is extended with a low energy extra U(1) symmetry. In this model the μ problem is radiatively solved in an automatic way. The right-handed neutrino can be heavy and the seesaw mechanism will produce the small neutrino mass which makes the MSW solution applicable to the solar neutrino problem. We search a parameter region which has the favorable feature for the radiative symmetry breaking at the weak scale. A rather wide parameter region is found to be allowed. Although there are certain dependences on the soft supersymmetry breaking parameters in the estimation of masses of various fields, the upper bound of the extra Z boson mass is estimated to be mZ2≤2000 GeV for a top mass range 150 GeV ≤mt≤190 GeV within a suitable parameter region (m0<1 TeV and m1/2<200 GeV ). Some phenomenological features of the extra Z boson are also presented.

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14

Adachi, S. "Inclusive searches for squarks and gluinos with the ATLAS detector." EPJ Web of Conferences 182 (2018): 02001. http://dx.doi.org/10.1051/epjconf/201818202001.

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Despite the absence of experimental evidence, the weak scale supersymmetry remains as one of the best motivated and studied theoretical models beyond the Standard Model. This article summarises recent ATLAS results on inclusive searches for squarks and gluinos in R-parity conserving SUSY scenarios, including third generation squarks produced in the decay of gluinos. The searches involve final states containing jets, missing transverse momentum with and without a light lepton. No significance excess above the Standard Model prediction is observed and exclusion limits are set on 2-dimensional mass planes of benchmark signal models.

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15

Burgess, C. P., Danielle Dineen, and F. Quevedo. "Yoga Dark Energy: natural relaxation and other dark implications of a supersymmetric gravity sector." Journal of Cosmology and Astroparticle Physics 2022, no. 03 (March 1, 2022): 064. http://dx.doi.org/10.1088/1475-7516/2022/03/064.

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Abstract We construct a class of 4D 'yoga' (naturally relaxed) models for which the gravitational response of heavy-particle vacuum energies is strongly suppressed. The models contain three ingredients: (i) a relaxation mechanism driven by a scalar field (the 'relaxon'), (ii) a very supersymmetric gravity sector coupled to the Standard Model in which supersymmetry is non-linearly realised, and (iii) an accidental approximate scale invariance expressed through the presence of a low-energy dilaton supermultiplet. All three are common in higher-dimensional and string constructions and although none suffices on its own, taken together they can dramatically suppress the net vacuum-energy density. The dilaton's vev τ determines the weak scale M W ∼ M p/√τ. We compute the potential for τ and find it can be stabilized in a local de Sitter minimum at sufficiently large field values to explain the size of the electroweak hierarchy, doing so using input parameters no larger than O(60) because the relevant part of the scalar potential arises as a rational function of lnτ. The de Sitter vacuum energy at the minimum is order c M 8 W α 1/τ 4, with a coefficient c ≪ 𝒪(M W -4). We discuss ways to achieve c ∼ 1/M p 4 as required by observations. Scale invariance implies the dilaton couples to matter like a Brans-Dicke scalar with coupling large enough to be naively ruled out by solar-system tests of gravity. Yet because it comes paired with an axion it can evade fifth-force bounds through the novel screening mechanism described in arXiv:2110.10352. Cosmological axio-dilaton evolution predicts a natural quintessence model for Dark Energy, whose evolution might realize recent proposals to resolve the Hubble tension, and whose axion contributes to Dark Matter. We summarize inflationary implications and some remaining challenges, including the unusual supersymmetry breaking regime used and the potential for UV completions of our approach.

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16

DIMOPOULOS, SAVAS, SHAMIT KACHRU, NEMANJA KALOPER, ALBION LAWRENCE, and EVA SILVERSTEIN. "GENERATING SMALL NUMBERS BY TUNNELING IN MULTI-THROAT COMPACTIFICATIONS." International Journal of Modern Physics A 19, no. 16 (June 30, 2004): 2657–704. http://dx.doi.org/10.1142/s0217751x04018075.

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A generic F-theory compactification containing many D3 branes develops multiple brane throats. The interaction of observers residing inside different throats involves tunneling suppression and as a result, is very weak. This suggests a new mechanism for generating small numbers in Nature. One application is to the hierarchy problem: large supersymmetry breaking near the unification scale inside a shallow throat causes TeV-scale SUSY-breaking inside the standard-model throat. Another application, inspired by nuclear-decay, is in designing naturally long-lived particles: a cold dark matter particle residing near the standard model brane decays to an approximate CFT-state of a longer throat within a Hubble time. This suggests that most of the mass of the universe today could consist of CFT-matter and may soften structure formation at sub-galactic scales. The tunneling calculation demonstrates that the coupling between two throats is dominated by higher dimensional modes and consequently is much larger than a naive application of holography might suggest.

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17

Frampton, Paul H. "Searching for dark matter constituents with many solar masses." Modern Physics Letters A 31, no. 16 (May 27, 2016): 1650093. http://dx.doi.org/10.1142/s0217732316500930.

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Searches for dark matter (DM) constituents are presently mainly focused on axions and weakly interacting massive particle (WIMPs) despite the fact that far higher mass constituents are viable. We discuss and dispute whether axions exist and those arguments for WIMPs which arise from weak scale supersymmetry. We focus on the highest possible masses and argue that, since if they constitute all DM, they cannot be baryonic, they must uniquely be primordial black holes. Observational constraints require them to be of intermediate masses mostly between ten and a hundred thousand solar masses. Known search strategies for such PIMBHs include wide binaries, cosmic microwave background (CMB) distortion and, most promisingly, extended microlensing experiments.

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18

CHOI, KANG-SIN. "INTERSECTING BRANE WORLD FROM TYPE I COMPACTIFICATION." International Journal of Modern Physics A 22, no. 19 (July 30, 2007): 3169–200. http://dx.doi.org/10.1142/s0217751x07036786.

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We elaborate that general intersecting brane models on orbifolds are obtained from type I string compactifications and their T-duals. Symmetry breaking and restoration occur via recombination and parallel separation of branes, preserving supersymmetry. The Ramond–Ramond tadpole cancellation and the toron quantization constrain the spectrum as a branching of the adjoints of SO(32), up to orbifold projections. Since the recombination changes the gauge coupling, the single gauge coupling of type I could give rise to different coupling below the unification scale. This is due to the nonlocal properties of the Dirac–Born–Infeld action. The desirable weak mixing angle sin 2θW = 3/8 is naturally explained by embedding the quantum numbers to those of SO(10).

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19

Kumar, Piyush. "Compactified string theories — Generic predictions for particle physics." International Journal of Modern Physics A 30, no. 03 (January 30, 2015): 1530019. http://dx.doi.org/10.1142/s0217751x15300197.

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In recent years it has been realized that in string/M theories compactified to four dimensions which satisfy cosmological constraints, it is possible to make some generic predictions for particle physics: a nonthermal cosmological history before primordial nucleosynthesis, a scale of supersymmetry breaking which is "high" as in gravity mediation, and scalar superpartners too heavy to be produced at the LHC (although gluino production is predicted in many cases). When the matter and gauge spectrum below the compactification scale is that of the MSSM, a robust prediction of about 125 GeV for the Higgs boson mass, as well as predictions for future precision measurements, can be made. As a prototypical example, M theory compactified on a manifold of G2 holonomy leads to a good candidate for our "string vacuum", with the TeV scale emerging from the Planck scale, a de Sitter vacuum, robust electroweak symmetry breaking, and solutions of the weak and strong CP problems. In this article we review how these and other results are derived, from the key theoretical ideas to the final phenomenological predictions.

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20

ACHARYA, BOBBY SAMIR, GORDON KANE, and PIYUSH KUMAR. "COMPACTIFIED STRING THEORIES — GENERIC PREDICTIONS FOR PARTICLE PHYSICS." International Journal of Modern Physics A 27, no. 12 (May 4, 2012): 1230012. http://dx.doi.org/10.1142/s0217751x12300128.

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In recent years it has been realized that in string/M theories compactified to four dimensions which satisfy cosmological constraints, it is possible to make some generic predictions for particle physics and dark matter: a nonthermal cosmological history before primordial nucleosynthesis, a scale of supersymmetry breaking which is "high" as in gravity mediation, scalar superpartners too heavy to be produced at the LHC (although gluino production is expected in many cases), and a significant fraction of dark matter in the form of axions. When the matter and gauge spectrum below the compactification scale is that of the MSSM, a robust prediction of about 125 GeV for the Higgs boson mass, predictions for various aspects of dark matter physics, as well as predictions for future precision measurements, can be made. As a prototypical example, M theory compactified on a manifold of G2 holonomy leads to a good candidate for our "string vacuum," with the TeV scale emerging from the Planck scale, a de Sitter vacuum, robust electroweak symmetry breaking, and solutions of the weak and strong CP problems. In this article we review how these and other results were derived, from the key theoretical ideas to the final phenomenological predictions.

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21

ADAMS, T., P. BATRA, L. BUGEL, L. CAMILLERI, J. M. CONRAD, A. DE GOUVÊA, P. H. FISHER, et al. "TERASCALE PHYSICS OPPORTUNITIES AT A HIGH STATISTICS, HIGH ENERGY NEUTRINO SCATTERING EXPERIMENT: NuSOnG." International Journal of Modern Physics A 24, no. 04 (February 10, 2009): 671–717. http://dx.doi.org/10.1142/s0217751x09043316.

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This paper presents the physics case for a new high-energy, ultra-high statistics neutrino scattering experiment, NuSOnG (Neutrino Scattering on Glass). This experiment uses a Tevatron-based neutrino beam to obtain over an order of magnitude higher statistics than presently available for the purely weak processes νμ + e- → νμ + e- and νμ + e- → νe + μ-. A sample of Deep Inelastic Scattering events which is over two orders of magnitude larger than past samples will also be obtained. As a result, NuSOnG will be unique among present and planned experiments for its ability to probe neutrino couplings to Beyond the Standard Model physics. Many Beyond Standard Model theories physics predict a rich hierarchy of TeV-scale new states that can correct neutrino cross-sections, through modifications of Zνν couplings, tree-level exchanges of new particles such as Z′'s, or through loop-level oblique corrections to gauge boson propagators. These corrections are generic in theories of extra dimensions, extended gauge symmetries, supersymmetry, and more. The sensitivity of NuSOnG to this new physics extends beyond 5 TeV mass scales. This paper reviews these physics opportunities.

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22

Pati, Jogesh C. "Advantages of unity with SU(4)-color: Reflections through neutrino oscillations, baryogenesis and proton decay." International Journal of Modern Physics A 32, no. 09 (March 23, 2017): 1741013. http://dx.doi.org/10.1142/s0217751x17410135.

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By way of paying tribute to Abdus Salam, I first recall the ideas of higher unification which the two of us introduced in 1972–73 to remove certain shortcomings in the status of particle physics prevailing then, and then present their current role in theory as well as experiments. These attempts initiated the idea of grand unification and provided the core symmetry-structure [Formula: see text]-color towards such a unification. Embodied with quark-lepton unification and left-right symmetry, the symmetry [Formula: see text] is uniquely chosen as being the minimal one that permits members of a family to belong to a single multiplet. The minimal extension of [Formula: see text] to a simple group is given by the attractive SO(10)-symmetry that was suggested a year later. The new concepts, and the many advantages introduced by this core symmetry (which are, of course, retained by SO(10) as well) are noted. These include explanations of the observed: (i) (rather weird) electroweak and color quantum numbers of the members of a family; (ii) quantization of electric charge; (iii) electron-proton charge-ratio being [Formula: see text]; (iv) the co-existence of quarks and leptons; (v) likewise that of the three basic forces — the weak, electromagnetic and strong; (vi) the non-trivial cancelation of the triangle anomalies within each family; and opening the door for (vii) the appealing concept of parity being an exact symmetry of nature at the fundamental level. In addition, as a distinguishing feature, both because of SU(4)-color and independently because of [Formula: see text] as well, the symmetry [Formula: see text] introduced, to my knowledge, for the first time in the literature: (viii) a new kind of matter — the right-handed (RH) neutrino [Formula: see text] — as a compelling member of each family, and together with it; (ix) (B-L) as a local symmetry. The RH neutrions — contrary to prejudices held in the 1970’s against neutrinos being massive and thereby against the existence of [Formula: see text]’s as well — have in fact turned out to be an asset. They are needed to (a) understand naturally the tiny mass-scales observed in neutrino oscillations by combining the seesaw mechanism together with the unification ideas based on the symmetry SU(4)-color, and also (b) to implement the attractive mechanism of baryogenesis via leptogenesis. The quantitative success of the attempts as regards understanding both (a) and (b) are discussed in Sec. 6. These provide a clear support simultaneously for the following three features: (i) the seesaw mechanism, (ii) the SU(4)-color route to higher unification based on a symmetry like SO(10) or a string-derived [Formula: see text] symmetry in 4D, as opposed to alternative symmetries like SU(5) or even [SU(3)]3, and (iii) the (B-L)-breaking scale being close to the unification scale [Formula: see text] GeV. The observed dramatic meeting of the three gauge couplings in the context of low-energy supersymmetry, at a scale [Formula: see text] GeV, providing strong evidence in favor of the ideas of both grand unification and supersymmetry, is discussed in Sec. 3. The implications of such a meeting in the context of string-unification are briefly mentioned. Weighing the possibility of a stringy origin of gauge coupling unification versus the familiar problem of doublet-triplet splitting in supersymmetric SO(10) (or SU(5)), I discuss the common advantages as well as relative merits and demerits of an effective SO(10) versus a string-derived [Formula: see text] symmetry in 4D. In Sec. 7, I discuss the hallmark prediction of grand unification, viz. proton decay, which is a generic feature of most models of grand unification. I present results of works carried out in collaboration with Babu and Wilczek and most recently with Babu and Tavartkiladze on expectations for decay modes and lifetimes for proton decay, including upper limits for such lifetimes, in the context of a well-motivated class of supersymmetric SO(10)-models. In view of such expectations, I stress the pressing need for having the next-generation large underground detectors — like DUNE and HyperKamiokande — coupled to long-baseline neutrino beams to search simultaneously with high sensitivity for (a) proton decay, (b) neutrino oscillations and (c) supernova neutrinos. It is remarked that the potential for major discoveries through these searches would be high. Some concluding remarks on the invaluable roles of neutrinos and especially of proton decay in probing physics at the highest energy scales are made in the last section. The remarkable success of a class of supersymmetric grand unification models (discussed here) in explaining a large set of distinct phenomena is summarized. Noticing such a success and yet its limitations in addressing some fundamental issues within its premises, such as an understanding of the origin of the three families, and most importantly, the realization of a well-understood unified quantum theory of gravity describing reality, some wishes are expressed on the possible emergence and the desirable role of a string-derived grand-unified bridge between string/M-theory in higher dimensions and the world of phenomena at low energies.

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23

Kane, Gordon. "Weak Scale Supersymmetry: From Superfields to Scattering Events; Theory and Phenomenology of Sparticles: An Account of Four-Dimensional N = 1 Supersymmetry in High Energy Physics; Modern Supersymmetry: Dynamics and Duality Weak Scale Supersymmetry: From Superfields to Scattering Events , Howard Baer and Xerxes Tata , Cambridge U. Press, New York, 2006. $80.00 (537 pp.). ISBN 0-521-85786-4 Theory and Phenomenology of Sparticles: An Account of Four-Dimensional N = 1 Supersymmetry in High Energy Physics , Manuel Drees , Rohini Godbole , and Probir Roy , World Scientific, Hackensack, NJ, 2005. $108.00, $64.00 paper (555 pp.). ISBN 981-02-3739-1, ISBN 981-256-531-0 paper Modern Supersymmetry: Dynamics and Duality , John Terning , Oxford U. Press, New York, 2006. $99.50 (324 pp.). ISBN 0-19-856763-4." Physics Today 59, no. 12 (December 2006): 62–63. http://dx.doi.org/10.1063/1.2435687.

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24

Cheung, Kingman, Cheng-Wei Chiang та Jeonghyeon Song. "A minimal supersymmetric scenario with only μ at the weak scale". Journal of High Energy Physics 2006, № 04 (24 квітня 2006): 047. http://dx.doi.org/10.1088/1126-6708/2006/04/047.

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25

FENG, JONATHAN L., ARVIND RAJARAMAN, and FUMIHIRO TAKAYAMA. "PROBING GRAVITATIONAL INTERACTIONS OF ELEMENTARY PARTICLES." International Journal of Modern Physics D 13, no. 10 (December 2004): 2355–59. http://dx.doi.org/10.1142/s0218271804006474.

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The gravitational interactions of elementary particles are suppressed by the Planck scale M*~1018 GeV and are typically expected to be far too weak to be probed by experiments. We show that, contrary to conventional wisdom, such interactions may be studied by particle physics experiments in the next few years. As an example, we consider conventional supergravity with a stable gravitino as the lightest supersymmetric particle. The next-lightest supersymmetric particle (NLSP) decays to the gravitino through gravitational interactions after about a year. This lifetime can be measured by stopping NLSPs at colliders and observing their decays. Such studies will yield a measurement of Newton's gravitational constant on unprecedentedly small scales, shed light on dark matter, and provide a window on the early universe.

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26

Bourilkov, Dimitri. "A Fresh Look at Gauge Coupling Unification." International Journal of Modern Physics A 20, no. 15 (June 20, 2005): 3328–30. http://dx.doi.org/10.1142/s0217751x05026479.

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The apparent unification of gauge couplings around 1016 GeV is one of the strong arguments in favor of Supersymmetric extensions of the Standard Model (SM). In this contribution a new analysis, using the latest experimental data, is performed. The strong coupling αs emerges as the key factor for evaluating the results of the fits, as the experimental and theoretical uncertainties in its measurements are substantially higher than for the electromagnetic and weak couplings. The present analysis pays special attention to numerical and statistical details. The results, combined with the current limits on the supersymmetric particle masses, favor a value for the SUSY scale ≲ 150 GeV and for αs = 0.118 - 0.119.

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27

Brax, Philippe, C. P. Burgess, and F. Quevedo. "Light axiodilatons: matter couplings, weak-scale completions and long-distance tests of gravity." Journal of Cosmology and Astroparticle Physics 2023, no. 08 (August 1, 2023): 011. http://dx.doi.org/10.1088/1475-7516/2023/08/011.

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Abstract We consider the physical implications of very light axiodilatons motivated by a novel mechanism to substantially reduce the vacuum energy proposed in 2110.10352. We address the two main problems concerning the light axiodilaton that appears in the low-energy limit, namely that the axion has a very low decay constant fa ∼ eV (as read from its kinetic term) and that the dilaton is subject to bounds that are relevant to tests of GR once ρ vac ≲ 10-80 Mp 4. We show that eV scale axion decay constants need not be a problem by showing how supersymmetric extra dimensions provide a sample unitarization for axion physics above eV scales for which non-anomalous matter/axiodilaton couplings can really have gravitational strength, showing how naive EFT reasoning can mistakenly overestimates axion interactions at eV. When axions really do couple strongly at eV scales we identify the dimensionless interaction in the UV completion that is also O(1), and how axion energy-loss bounds map onto known extra-dimensional constraints. We find a broad new class of exact exterior solutions to the vacuum axiodilaton equations and knowledge of axiodilaton-matter couplings also allows us to numerically search for interior solutions that match to known exterior solutions that can evade solar-system tests. We find no examples that do so, but also identify potential new candidate mechanisms for reducing the effective dilaton-matter coupling to gravitating objects without also undermining the underlying suppression of ρ vac.

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28

Kobayashi, Tatsuo, and Zhi-Zhong Xing. "A String-Inspired Ansatz for Quark Masses and Mixing." Modern Physics Letters A 12, no. 08 (March 14, 1997): 561–71. http://dx.doi.org/10.1142/s0217732397000583.

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We propose a simple but realistic pattern of quark mass matrices at the string scale, which can be derived from orbifold models of superstring theory with no use of gauge symmetries. This pattern is left–right symmetric and preserves the structural parallelism between up and down quark sectors. Its phenomenological consequences on flavor mixing and CP-violation are confronted with current experiments at the weak scale by using the renormalization group equations in the framework of minimal supersymmetric standard model. We find that good agreement is achievable without fine-tuning.

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29

LI, TIANJUN, and WEI LIAO. "LOW ENERGY GAUGE UNIFICATION THEORY." Modern Physics Letters A 17, no. 36 (November 30, 2002): 2393–407. http://dx.doi.org/10.1142/s0217732302009131.

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Because of the problems arising from the fermion unification in the traditional grand unified theory and the mass hierarchy between the four-dimensional Planck scale and weak scale, we suggest the low energy gauge unification theory with low high-dimensional Planck scale. We discuss the nonsupersymmetric SU(5) model on M4 × S1/Z2 × S1/Z2 and the supersymmetric SU(5) model on M4 × S1/(Z2 × Z2′) × S1/(Z2 × Z2′). The SU(5) gauge symmetry is broken by the orbifold projection for the zero modes, and the gauge unification is accelerated due to the SU(5) asymmetric light KK states. In our models, we forbid the proton decay, still keep the charge quantization, and automatically solve the fermion mass problem. We also comment on the anomaly cancellation and other possible scenarios for low energy gauge unification.

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30

ZWIRNER, FABIO. "THE HIGGS PUZZLE: EXPERIMENT AND THEORY." International Journal of Modern Physics A 17, no. 23 (September 20, 2002): 3300–3317. http://dx.doi.org/10.1142/s0217751x02012740.

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The present experimental and theoretical knowledge of the physics of electroweak symmetry breaking is reviewed. Data still favor a light Higgs boson, of a kind that can be comfortably accommodated in the Standard Model or in its Minimal Supersymmetric extension, but exhibit a non-trivial structure that leaves some open questions. The available experimental information may still be reconciled with the absence of a light Higgs boson, but the price to pay looks excessive. Recent theoretical ideas, linking the weak scale with the size of possible extra spatial dimensions, are briefly mentioned. It is stressed once more that experiments at high-energy colliders, such as the Tevatron and the LHC, are the crucial tool for eventually solving the Higgs puzzle.

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31

Wang, Fei, Wenyu Wang, Lei Wu, Jin Min Yang, and Mengchao Zhang. "Probing degenerate heavy Higgs bosons in NMSSM with vector-like particles." International Journal of Modern Physics A 32, no. 33 (November 30, 2017): 1745005. http://dx.doi.org/10.1142/s0217751x17450051.

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In this work, we investigate the degenerate heavy Higgs bosons in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by introducing vector-like particles. Such an extension is well motivated from the top-down view since some grand unified theories usually predict the existence of singlet scalars and vector-like particles at weak scale. Under the constraints from the Large Hadron Collider (LHC) and dark matter experiments, we find that (1) the null results of searching for high mass resonances have tightly constrained the parameter space; (2) two degenerate heavy singlet Higgs bosons [Formula: see text] and [Formula: see text] can sizably decay to [Formula: see text] invisibly. Therefore, search for the monojet events through the process [Formula: see text] may further test our scenario at the future LHC.

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32

NIELSEN, H. B. "COMPLEX ACTION SUPPORT FROM COINCIDENCES OF COUPLINGS." International Journal of Modern Physics E 20, no. 09 (September 2011): 2049–75. http://dx.doi.org/10.1142/s0218301311019726.

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Our model (Refs. 1–7) with a complex action in a functional integral formulation with path integrals extending over all times, both past and future, is reviewed. Several numerical relations between coupling constants are presented as supporting evidence. The new evidence is that several more hitherto unexplained coincidences are explained by our model: (1) The "scale problem" is solved because the Higgs field expectation value is predicted to be very small compared to say some fundamental scale, that might be the Planck scale. (2) The Higgs VEV need not be just zero, but rather is predicted to be so that the running top-quark Yukawa coupling just is about to be unity at this scale; in this way the (weak) scale easily becomes "exponentially small." Instead of the top-Yukawa we should rather say the highest flavor Yukawa coupling here. These predictions are only achieved by allowing the principle of minimization of the imaginary part of the action SI(history) to a certain extent adjust some coupling constants in addition to the initial conditions. If supersymmetric partners are not found at LHC it would strengthen the need for a "solution" to the hierarchy problem in our direction of an explanation via a fine-tuning scheme inside the Standard Model, from say minimizing "the imaginary part of the action" in our complex action model.

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33

de Martino, Ivan. "Giant low-surface-brightness dwarf galaxy as a test bench for MOdified Gravity." Monthly Notices of the Royal Astronomical Society 493, no. 2 (February 17, 2020): 2373–76. http://dx.doi.org/10.1093/mnras/staa460.

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ABSTRACT The lack of detection of supersymmetric particles is leading to look at alternative avenues for explaining dark matter’s effects. Among them, modified theories of gravity may play an important role accounting even for both dark components needed in the standard cosmological model. Scalar–tensor–vector gravity theory has been proposed to resolve the dark matter puzzle. Such a modified gravity model introduces, in its weak field limit, a Yukawa-like correction to the Newtonian potential, and is capable to explain most of the phenomenology related to dark matter at scale of galaxies and galaxy clusters. Nevertheless, some inconsistencies appear when studying systems that are supposed to be dark matter dominated such as dwarf galaxies. In this sense, Antlia II, an extremely diffuse galaxy which has been recently discovered in Gaia’s second data release, may serve to probe the aforementioned theory against the need for invoking dark matter. Our analysis shows several inconsistencies and leads to argue that MOdified Gravity may not be able to shed light on the intriguing nature of dark matter.

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34

Iyer, Abhishek M. "Flavour physics and extra-dimensions." EPJ Web of Conferences 179 (2018): 01006. http://dx.doi.org/10.1051/epjconf/201817901006.

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Randall-Sundrum (RS) model of warped extra-dimensions were originally proposed to explain the Planck-weak scale hierarchy. It was soon realised that modifications of the original setup, by introducing the fields in the bulk, has several interesting features. In particular it imbues a rich flavour structure to the fermionic sector thereby offering an understanding of the Yukawa hierarchy problem. This construction is also useful in explaining the recently observed deviations in the decay of the B mesons. We consider two scenarios to this effect : A) Right handed muon fields coupled more to NP that the corresponding muon doublets (unorthodox case). Non-universality exists in the right handed sector. B) Standard scenario with anomalies explained primarily by non-universal couplings to the lepton doublets. Further, we establish correlation with the parameter space consistent with the flavour anomalies in the neutral current sector and obtain predictions for rare K- decay which are likely to be another candle for NP with increased precision. The prediction for rare K- decays are different according to the scenario, thereby serving as a useful discriminatory tool. We also discussthe large flavour violation in the lepton sector and present an example with the implementation of bulk leptonic MFV which is essential to realize the model with low KK scales. Further we consider a radical solution, called GUT RS models, where the RS geometry can work as theory of flavour in the absence of flavour symmetries. In this case the low energy brane corresponds to the GUT scale as a result of which RS is no longer solution to the gauge hierarchy problem. The Kaluza Klein (KK) modes in this setup are naturally heavy due to which the low energy constraints can be easily avoided. We use this framework to discuss the supersymmetric version of the RS model and provide means to test this scenario by considering rare lepton decays like τ → μγ.

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35

Cribiori, Niccolò, and Gianguido Dall’Agata. "Weak gravity versus scale separation." Journal of High Energy Physics 2022, no. 6 (June 2022). http://dx.doi.org/10.1007/jhep06(2022)006.

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Abstract We give evidence that fully supersymmetric Anti-de Sitter vacua of extended supergravity with a residual gauge group containing an abelian factor cannot be scale separated as a consequence of the weak gravity conjecture. We prove this for N = 2 and N = 8 supergravity and we explain how our argument applies also to vacua with partially broken, but extended residual supersymmetry. We finally discuss possible loopholes and especially how certain N = 1 models can evade our reasoning. Our results suggest that N = 0, 1 supersymmetry at the lagrangian level might be the most promising chances to obtain a truly four-dimensional effective description of quantum gravity.

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36

Luty, Markus A. "Weak Scale Supersymmetry without Weak Scale Supergravity." Physical Review Letters 89, no. 14 (September 17, 2002). http://dx.doi.org/10.1103/physrevlett.89.141801.

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37

Ellis, Sebastian A. R., Tony Gherghetta, Kunio Kaneta, and Keith A. Olive. "New weak-scale physics from SO(10) with high-scale supersymmetry." Physical Review D 98, no. 5 (September 11, 2018). http://dx.doi.org/10.1103/physrevd.98.055009.

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38

Baer, Howard, Vernon Barger, Dakotah Martinez, and Shadman Salam. "Practical naturalness and its implications for weak scale supersymmetry." Physical Review D 108, no. 3 (August 29, 2023). http://dx.doi.org/10.1103/physrevd.108.035050.

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39

Baer, Howard, Vernon Barger, Dakotah Martinez, and Shadman Salam. "Radiative natural supersymmetry emergent from the string landscape." Journal of High Energy Physics 2022, no. 3 (March 2022). http://dx.doi.org/10.1007/jhep03(2022)186.

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Abstract In string theory with flux compactifications, anthropic selection for structure formation from a discretuum of vacuum energy values provides at present our only understanding of the tiny yet positive value of the cosmological constant. We apply similar reasoning to a toy model of the multiverse restricted to vacua with the MSSM as the low energy effective theory. Here, one expects a statistical selection favoring large soft SUSY breaking terms leading to a derived value of the weak scale in each pocket universe (with appropriate electroweak symmetry breaking) which differs from the weak scale as measured in our universe. In contrast, the SUSY preserving μ parameter is selected uniformly on a log scale as is consistent with the distribution of SM fermion masses: this favors smaller values of μ. An anthropic selection of the weak scale to within a factor of a few of our measured value — in order to produce complex nuclei as we know them (atomic principle) — provides statistical predictions for Higgs and sparticle masses in accord with LHC measurements. The statistical selection then more often leads to (radiatively-driven) natural SUSY models over the Standard Model or finely-tuned SUSY models such as mSUGRA/CMSSM, split, mini-split, spread, high scale or PeV SUSY. The predicted Higgs and superparticle spectra might be testable at HL-LHC or ILC via higgsino pair production but is certainly testable at higher energy hadron colliders with $$ \sqrt{s} $$ s ∼ 30–100 TeV.

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40

Klaewer, Daniel, Seung-Joo Lee, Timo Weigand, and Max Wiesner. "Quantum corrections in 4d N = 1 infinite distance limits and the weak gravity conjecture." Journal of High Energy Physics 2021, no. 3 (March 2021). http://dx.doi.org/10.1007/jhep03(2021)252.

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Abstract We study quantum corrections in four-dimensional theories with N = 1 supersymmetry in the context of Quantum Gravity Conjectures. According to the Emergent String Conjecture, infinite distance limits in quantum gravity either lead to decompactification of the theory or result in a weakly coupled string theory. We verify this conjecture in the framework of N = 1 supersymmetric F-theory compactifications to four dimensions including perturbative α′ as well as non-perturbative corrections. After proving uniqueness of the emergent critical string at the classical level, we show that quantum corrections obstruct precisely those limits in which the scale of the emergent critical string would lie parametrically below the Kaluza-Klein scale. Limits in which the tension of the asymptotically tensionless string sits at the Kaluza-Klein scale, by contrast, are not obstructed.In the second part of the paper we study the effect of quantum corrections for the Weak Gravity Conjecture away from the strict weak coupling limit. We propose that gauge threshold corrections and mass renormalisation effects modify the super-extremality bound in four dimensions. For the infinite distance limits in F-theory the classical super-extremality bound is generically satisfied by a sublattice of states in the tower of excitations of an emergent heterotic string. By matching the F-theory α′-corrections to gauge threshold corrections of the dual heterotic theory we predict how the masses of this tower must be renormalised in order for the Weak Gravity Conjecture to hold at the quantum level.

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41

Farakos, Fotis, George Tringas, and Thomas Van Riet. "No-scale and scale-separated flux vacua from IIA on G2 orientifolds." European Physical Journal C 80, no. 7 (July 2020). http://dx.doi.org/10.1140/epjc/s10052-020-8247-5.

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Abstract We discuss flux compactifications of IIA string theory on G2 holonomy spaces with O2/O6-planes to three dimensions and find two classes of solutions: (1) No-scale Minkowski vacua from NSNS 3-form fluxes and RR 4-form fluxes. (2) By adding Romans mass we find AdS$$_3$$3 vacua for which the AdS scale can be decoupled completely from the KK scale while the solution is at tunable weak coupling and large volume. For the AdS$$_3$$3 vacuum we only have a proper 3D description (i.e. smeared orientifold description) of the solution like the 4D analogue of IIA moduli stabilization from fluxes and O6-planes. This 3D description reveals that moduli with non-compact moduli spaces can be stabilized at the classical level. For both types of vacua we can have supersymmetry or not.

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42

Montero, Miguel, Martin Roček, and Cumrun Vafa. "Pure supersymmetric AdS and the Swampland." Journal of High Energy Physics 2023, no. 1 (January 18, 2023). http://dx.doi.org/10.1007/jhep01(2023)094.

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Abstract We point out that pure supergravity theories in AdS with enough supersymmetry lead, upon taking the large radius limit, to flat space quantum gravities with a nonperturbatively exact global symmetry, and are therefore in the Swampland. The argument applies to any AdS supergravity with gauged R-symmetry group, including truncations of most well known examples, such as AdS5 without the S5 or AdS4 without the S7. This demonstrates that extreme scale separation, at least with enough supersymmetry, is not realizable. Moreover pure AdS theories are also in conflict with some other Swampland principles including the Weak Gravity Conjecture and the (generalized) Distance Conjecture.

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43

Baer, Howard, Vernon Barger, and Michael Savoy. "Upper bounds on sparticle masses from naturalness or how to disprove weak scale supersymmetry." Physical Review D 93, no. 3 (February 16, 2016). http://dx.doi.org/10.1103/physrevd.93.035016.

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44

Chan, Kwok Lung, Utpal Chattopadhyay, and Pran Nath. "Naturalness, weak scale supersymmetry, and the prospect for the observation of supersymmetry at the Fermilab Tevatron and at the CERN LHC." Physical Review D 58, no. 9 (September 23, 1998). http://dx.doi.org/10.1103/physrevd.58.096004.

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45

Cota, Cesar Fierro, Alessandro Mininno, Timo Weigand, and Max Wiesner. "The asymptotic Weak Gravity Conjecture for open strings." Journal of High Energy Physics 2022, no. 11 (November 11, 2022). http://dx.doi.org/10.1007/jhep11(2022)058.

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Abstract We investigate the asymptotic Tower Weak Gravity Conjecture in weak coupling limits of open string theories with minimal supersymmetry in four dimensions, focusing for definiteness on gauge theories realized on 7-branes in F-theory. Contrary to expectations, we find that not all weak coupling limits contain an obvious candidate for a tower of states marginally satisfying the super-extremality bound. The weak coupling limits are classified geometrically in the framework of EFT string limits and their generalizations. We find three different classes of weak coupling limits, whose physics is characterized by the ratio of the magnetic weak gravity scale and the species scale. The four-dimensional Tower Weak Gravity Conjecture is satisfied by the (non-BPS) excitations of the weakly coupled EFT string only in emergent string limits, where the EFT string can be identified with a critical (heterotic) string. All other weak coupling limits lead to a decompactification either to an in general strongly coupled gauge theory coupled to gravity or to a defect gauge theory decoupling from the gravitational bulk, in agreement with the absence of an obvious candidate for a marginally super-extremal tower of states.

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46

Baer, Howard, Vernon Barger, and Dakotah Martinez. "Comparison of SUSY spectra generators for natural SUSY and string landscape predictions." European Physical Journal C 82, no. 2 (February 2022). http://dx.doi.org/10.1140/epjc/s10052-022-10141-2.

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AbstractModels of natural supersymmetry give rise to a weak scale $$m_{weak}\sim m_{W,Z,h}\sim 100$$ m weak ∼ m W , Z , h ∼ 100 GeV without any (implausible) finetuning of independent contributions to the weak scale. These models, which exhibit radiatively driven naturalness (RNS), are expected to arise from statistical analysis of the string landscape wherein large soft terms are favored, but subject to a not-too-large value of the derived weak scale in each pocket universe of the greater multiverse. The string landscape picture then predicts, using the Isajet SUSY spectra generator Isasugra, a statistical peak at $$m_h\sim 125$$ m h ∼ 125 GeV with sparticles generally beyond current LHC search limits. In this paper, we investigate how well these conclusions hold up using other popular spectra generators: SOFTSUSY, SPHENO and SUSPECT (SSS). We built a computer code DEW4SLHA which operates on SUSY Les Houches Accord files to calculate the associated electroweak naturalness measure $$\Delta _{EW}$$ Δ EW . The SSS generators tend to yield a Higgs mass peak $$\sim 125$$ ∼ 125 –127 GeV with a superparticle mass spectra rather similar to that generated by Isasugra. In an Appendix, we include loop corrections to $$\Delta _{EW}$$ Δ EW in a more standard notation.

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47

Joshipura, Anjan S., and Ketan M. Patel. "Weak scale right-handed neutrino as pseudo-Goldstone fermion of spontaneously broken $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$." Journal of High Energy Physics 2021, no. 9 (September 2021). http://dx.doi.org/10.1007/jhep09(2021)115.

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Abstract Possibility of a Right-Handed (RH) neutrino being a Goldstone fermion of a spontaneously broken global U(1) symmetry in a supersymmetric theory is considered. This fermion obtains mass from the supergravity effects leading to a RH neutrino at the electroweak scale with a mass similar to the gravitino mass. A prototype model realizing this scenario contains just three gauge singlet superfields needed for the type I seesaw mechanism. Masses of the other two neutrinos are determined by the U(1) breaking scale which too can be around the electroweak scale. Light neutrinos obtain their masses in this scenario through (a) mixing with the RH neutrinos (type I seesaw), (b) mixing with neutralinos (R-parity breaking), (c) indirectly through mixing of the RH neutrinos with neutralinos, and (d) radiative corrections. All these contributions are described by the same set of a small number of underlying parameters and provide a very constrained and predictive framework for the neutrino masses which is investigated in detail for various choices of U(1) symmetries. It is found that flavour independent U(1) symmetries cannot describe neutrino masses if the soft supersymmetry breaking terms are flavour universal and one needs to consider flavour dependent symmetries. Considering a particular example of Lμ− Lτ symmetry, it is shown that viable neutrino masses and mixing can be obtained without introducing any flavour violation in the soft sector. The leptonic couplings of Majoron are worked out in the model and shown to be consistent with various laboratory, astrophysical and cosmological constraints. The neutrino data allows sizeable couplings between the RH neutrinos and Higgsinos which can be used to probe the pseudo-Goldstone fermion at colliders through its displaced decay vertex.

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48

Liu, Yi, Stefano Moretti, and Harri Waltari. "Measuring neutrino dynamics in NMSSM with a right-handed sneutrino LSP at the ILC." Journal of High Energy Physics 2022, no. 1 (January 2022). http://dx.doi.org/10.1007/jhep01(2022)034.

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Abstract We study the possibility of measuring neutrino Yukawa couplings in the Next-to-Minimal Supersymmetric Standard Model with right-handed neutrinos (NMSSMr) when the lightest right-handed sneutrino is the Dark Matter (DM) candidate, by exploiting a ‘dijet + dilepton + Missing Transverse Energy’ (MET or "Image missing") signature. We show that, contrary to the miminal realisation of Supersymmetry (SUSY), the MSSM, wherein the DM candidate is typically a much heavier (fermionic) neutralino state, this extended model of SUSY offers one with a much lighter (bosonic) state as DM that can then be produced at the next generation of e+e− colliders with energies up to 500 GeV or so. The ensuing signal, energing from chargino pair production and subsequent decay, is extremely pure so it also affords one with the possibility of extracting the Yukawa parameters of the (s)neutrino sector. Altogether, our results serve the purpose of motivating searches for light DM signals at such machines, where the DM candidate can have a mass around the Electro-Weak (EW) scale.

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49

Bloch, Itay M., Csaba Csáki, Michael Geller та Tomer Volansky. "Crunching away the cosmological constant problem: dynamical selection of a small Λ". Journal of High Energy Physics 2020, № 12 (грудень 2020). http://dx.doi.org/10.1007/jhep12(2020)191.

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Abstract We propose a novel explanation for the smallness of the observed cosmological constant (CC). Regions of space with a large CC are short lived and are dynamically driven to crunch soon after the end of inflation. Conversely, regions with a small CC are metastable and long lived and are the only ones to survive until late times. While the mechanism assumes many domains with different CC values, it does not result in eternal inflation nor does it require a long period of inflation to populate them. We present a concrete dynamical model, based on a super-cooled first order phase transition in a hidden conformal sector, that may successfully implement such a crunching mechanism. We find that the mechanism can only solve the CC problem up to the weak scale, above which new physics, such as supersymmetry, is needed to solve the CC problem all the way to the UV cutoff scale. The absence of experimental evidence for such new physics already implies a mild little hierarchy problem for the CC. Curiously, in this approach the weak scale arises as the geometric mean of the temperature in our universe today and the Planck scale, hinting at a new “CC miracle”, motivating new physics at the weak scale independent of electroweak physics. We further predict the presence of new relativistic degrees of freedom in the CFT that should be visible in the next round of CMB experiments. Our mechanism is therefore predictive and experimentally falsifiable.

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50

Baer, Howard, Vernon Barger, Dakotah Martinez, and Shadman Salam. "Fine-tuned vs. natural supersymmetry: what does the string landscape predict?" Journal of High Energy Physics 2022, no. 9 (September 16, 2022). http://dx.doi.org/10.1007/jhep09(2022)125.

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Abstract A vast array of (metastable) vacuum solutions arise from string compactifications, each leading to different 4-d laws of physics. The space of these solutions, known as the string landscape, allows for an environmental solution to the cosmological constant problem. We examine the possibility of an environmental solution to the gauge hierarchy problem. We argue that the landscape favors softly broken supersymmetric models over particle physics models containing quadratic divergences, such as the Standard Model. We present a scheme for computing relative probabilities for supersymmetric models to emerge from the landscape. The probabilities are related to the likelihood that the derived value of the weak scale lies within the Agrawal et al. (ABDS) allowed window of values leading to atoms as we know them. This then favors natural SUSY models over unnatural (SUSY and other) models via a computable probability measure.

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