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Статті в журналах з теми "Quarks"

Автор: Grafiati

Опубліковано: 4 червня 2021

Оновлено: 9 листопада 2024

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1

Ball, Richard D., Alessandro Candido, Juan Cruz-Martinez, Stefano Forte, Tommaso Giani, Felix Hekhorn, Kirill Kudashkin, Giacomo Magni, and Juan Rojo. "Evidence for intrinsic charm quarks in the proton." Nature 608, no. 7923 (August 17, 2022): 483–87. http://dx.doi.org/10.1038/s41586-022-04998-2.

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Анотація:

AbstractThe theory of the strong force, quantum chromodynamics, describes the proton in terms of quarks and gluons. The proton is a state of two up quarks and one down quark bound by gluons, but quantum theory predicts that in addition there is an infinite number of quark–antiquark pairs. Both light and heavy quarks, whose mass is respectively smaller or bigger than the mass of the proton, are revealed inside the proton in high-energy collisions. However, it is unclear whether heavy quarks also exist as a part of the proton wavefunction, which is determined by non-perturbative dynamics and accordingly unknown: so-called intrinsic heavy quarks1. It has been argued for a long time that the proton could have a sizable intrinsic component of the lightest heavy quark, the charm quark. Innumerable efforts to establish intrinsic charm in the proton2 have remained inconclusive. Here we provide evidence for intrinsic charm by exploiting a high-precision determination of the quark–gluon content of the nucleon3 based on machine learning and a large experimental dataset. We disentangle the intrinsic charm component from charm–anticharm pairs arising from high-energy radiation4. We establish the existence of intrinsic charm at the 3-standard-deviation level, with a momentum distribution in remarkable agreement with model predictions1,5.We confirm these findings by comparing them to very recent data on Z-boson production with charm jets from the Large Hadron Collider beauty (LHCb) experiment6.

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2

SHI, X. H., G. L. MA, Y. G. MA, X. Z. CAI та J. H. CHEN. "“TEMPERATURE” FLUCTUATION AND HEAT CAPACITIES OF QUARKS AND π MESON". International Journal of Modern Physics E 16, № 07n08 (серпень 2007): 1912–16. http://dx.doi.org/10.1142/s0218301307007222.

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Анотація:

Specific heat capacities of π meson and different quarks after parton cascade AMPT model in Au + Au collisions at [Formula: see text] have been tentatively extracted from the event-by-event temperature fluctuations in the region of low transverse mass. The specific heat capacity of π meson shows a slight dropping trend with increasing impact parameter. The specific heat capacities of different quarks increase with the mass of quark, and the sum of up and down quark's specific heat capacities was found to be approximately equal to that of π meson.

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3

ANTUNES, ANTONIO CARLOS BAPTISTA, and LEILA JORGE ANTUNES. "DIQUARK FORMATION IN ANGULAR-MOMENTUM-EXCITED BARYONS." International Journal of Modern Physics A 24, no. 10 (April 20, 2009): 1987–94. http://dx.doi.org/10.1142/s0217751x09043249.

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Анотація:

Diquarks, or metastable clusters of two quarks inside baryons, are shown to be produced by angular momentum excitation. In baryons with a light quark and two heavy quarks with large angular momentum (L>2), the centrifugal barrier that appears in the rotation frame of the two heavy quarks prevents the light quark from passing freely between the two heavy quarks. The light quark must tunnelize through this potential barrier, which gives rise to the clusters of a light and a heavy quark.

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4

Arghirescu, Marius. "A hybrid model of constituent quarks." Physics & Astronomy International Journal 6, no. 3 (September 20, 2022): 109–17. http://dx.doi.org/10.15406/paij.2022.07.00262.

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Анотація:

The paper presents a hybrid model of constituent quark which considers the preonic structure based on z0 (34 me)-preon, specific to the previously published cold genesis theory (CGT) of the author and basic concepts of the S.M. which seem experimentally sustained, explaining the constituent quarks forming from current quarks and “gammonic” gluols –in concordance with the experimentally evidenced possibility of paired quarks forming from relativist jets of negatrons and positrons, by considering that the negatrons and positrons can form ‘gammonic’ “gluols” and thereafter- current and constituent quarks, by the magnetic and electric interactions between the paired quasielectrons (degenerate electrons), which can explain the constituent u- quark’s stability until the critical temperature 2x1012 K, without the concepts of “color charge” and of “virtual” gluon/boson. The resulted hybrid model can also explain why in strong interactions the sum rule can be applied correspondent with the transferring of some quarks from an interacting particle to another with the entire or almost entire their constituent mass. Also, it suggests that the mechanism of paired current u-quarks forming from gluons, used by the S. M., can be plausible in conformity with the mass conservation law only if the quantum vacuum contains real thermalized “gammons” considered as (e+e-)*-pairs of degenerate electrons.

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5

ANTUNES, ANTONIO CARLOS BAPTISTA, and LEILA JORGE ANTUNES. "ABSENCE OF DIQUARKS IN S-WAVE BARYONS." International Journal of Modern Physics A 22, no. 25 (October 10, 2007): 4709–16. http://dx.doi.org/10.1142/s0217751x07037950.

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Анотація:

We analyze the dynamics of diquark formation in baryons containing one light and two heavy quarks. Due to the slower motion of the heavy quarks, we consider the motion of the light quark in a reference frame fixed in the two heavy ones. The potential of the light quark interacting with the two heavy quarks is derived from the quark–antiquark potential in mesons. This potential has a repulsive barrier between the two heavy quarks. A variational approach similar to that used in the study of the hydrogen molecule is applied to determine the two lowest energy eigenvalues and eigenfunctions of the light quark. The time-dependent wave function obtained describes the oscillation of the light quark along the direction defined by the two heavy quarks. We observe that the energy of this oscillating state is higher than the repulsive barrier between the two heavy quarks. There is no tunneling in the oscillation of the light quark, so we conclude that there is not formation of clusters or metastable states of a heavy and a light quark in this kind of baryons.

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6

Bhattacharyya, Trambak, Surasree Mazumder, and Raktim Abir. "Soft Gluon Radiation off Heavy Quarks beyond Eikonal Approximation." Advances in High Energy Physics 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/1298986.

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Анотація:

We calculate the soft gluon radiation spectrum off heavy quarks (HQs) interacting with light quarks (LQs) beyond small angle scattering (eikonality) approximation and thus generalize the dead-cone formula of heavy quarks extensively used in the literatures of Quark-Gluon Plasma (QGP) phenomenology to the large scattering angle regime which may be important in the energy loss of energetic heavy quarks in the deconfined Quark-Gluon Plasma medium. In the proper limits, we reproduce all the relevant existing formulae for the gluon radiation distribution off energetic quarks, heavy or light, used in the QGP phenomenology.

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7

KAUS, PETER, and SYDNEY MESHKOV. "A BCS QUARK MASS MATRIX." Modern Physics Letters A 03, no. 13 (October 1988): 1251–59. http://dx.doi.org/10.1142/s0217732388001501.

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Анотація:

The quark mass gap and quark mass hierarchy is obtained by introducing a BCS interaction among ur-quarks. A 3×3 quark mass matrix with equal matrix elements, i.e., with all ur-flavors interacting with the same strength, has eigenvalues 0, 0 and 3; both the quark charge −1/3 and charge +2/3 systems with one heavy quark and two almost massless quarks resemble these eigenvalues. The physical mass splittings between the two lightest quarks come from higher-order corrections to the mass matrix which are obtained by fitting the Kobayashi-Maskawa matrix VKM.

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8

FRITZSCH, H., and G. ELDAHOUMI. "CONSTITUENT QUARKS AND THE SPIN OF THE PROTON." Modern Physics Letters A 24, no. 27 (September 7, 2009): 2167–74. http://dx.doi.org/10.1142/s0217732309031788.

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Анотація:

The constituent quarks are interpreted as bound states, which have an internal structure. The quark distributions of the proton are related to those of the constituent quarks. The experiments support this hypothesis. Likewise the spin structure of the proton is related to the spin structure of the constituent quarks. We find that about 30% of the spin of a constituent quark is given by the valence quark, and 70% are provided by the gluons.

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9

Battistel, O. A., and G. Krein. "Quark Clustering and Chiral Symmetry Breaking in Nuclear Matter." Modern Physics Letters A 18, no. 32 (October 20, 2003): 2255–64. http://dx.doi.org/10.1142/s0217732303012040.

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Анотація:

Chiral symmetry breaking at finite baryon density is usually discussed in the context of quark matter, i.e. a system of deconfined quarks. Many systems like stable nuclei and neutron stars however have quarks confined within nucleons. In this paper we construct a Fermi sea of three-quark nucleon clusters and investigate the change of the quark condensate as a function of baryon density. We study the effect of quark clustering on the in-medium quark condensate and compare results with the traditional approach of modeling hadronic matter in terms of a Fermi sea of deconfined quarks.

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10

STROBEL, GEORGE L. "BARYON MAGNETIC MOMENTS AND SPIN DEPENDENT QUARK FORCES." International Journal of Modern Physics E 11, no. 01 (February 2002): 71–81. http://dx.doi.org/10.1142/s0218301302000697.

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Анотація:

The J=3/2 Δ, J=1/2 nucleon mass difference shows that quark energies can be spin dependent. It is natural to expect that quark wave functions also depend on spin. In the octet, such spin dependent forces lead to different wave functions for quarks with spin parallel or antiparallel to the nucleon spin. A two component Dirac equation wave function is used for the quarks assuming small current quark masses for the u and d quarks. Then, the neutron/proton magnetic moment ratio, the nucleon axial charge, and the spin content of the nucleon can all be simultaneously fit assuming isospin invariance between the u and d quarks, but allowing for spin dependent forces. The breakdown of the Coleman–Glashow sum rule for octet magnetic moments follows naturally in this Dirac approach as the bound quark energy also effects the magnetic moment. Empirically the bound quark energy increases with the number of strange quarks in the system. Allowing the strange quark wave function similar spin dependence predicts the magnetic moments of the octet, in close agreement with experiment. Differences between the octet and decuplet magnetic moments are also explained immediately with spin dependent wave functions.

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11

Tan, Z. G., and C. B. Yang. "Hadron formation from interaction among quarks." International Journal of Modern Physics E 24, no. 06 (June 2015): 1550044. http://dx.doi.org/10.1142/s0218301315500445.

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Анотація:

This paper deals with the hadronization process of quark system. A phenomenological potential is introduced to describe the interaction between a quark pair. The potential depends on the color charge of those quarks and their relative distances. Those quarks move according to classical equations of motion. Due to the color interaction, coloring quarks are separated to form color neutral clusters which are supposed to be the hadrons.

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12

McKellar, Bruce H. J. "ΔS = 0 weak interactions at the quark level". Canadian Journal of Physics 66, № 6 (1 червня 1988): 524–26. http://dx.doi.org/10.1139/p88-086.

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Анотація:

The calculation of short-distance gluon exchange corrections to the ΔS = 0 weak interaction at the quark level is described. Results are given for the coefficients of the 36 independent four-quark operators involving u, d, and s quarks explicitly, and for the 16 independent operators, which remain when s quarks are eliminated and only u and d quarks explicitly occur in the operators.

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13

Dobur, D., J. Knolle, G. Mestdach, and K. Skovpen. "Photon radiation effects in kinematic reconstruction of top quarks." Journal of Instrumentation 16, no. 12 (December 1, 2021): P12001. http://dx.doi.org/10.1088/1748-0221/16/12/p12001.

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Анотація:

Abstract Kinematic reconstruction of top quarks allows to define a set of kinematic observables relevant to various physics processes that involve top quarks and provides an additional handle for the suppression of background events. Radiation of photons in association with the top quarks alters the kinematics and the topology of the event, leading to visible systematic effects in measurable observables. The present study introduces an improved reconstruction of the top quark kinematics in the presence of photon radiation. The results are presented for processes with top quark pair production, as well as for singly-produced top quarks.

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14

Iakubovskii, Evgenii Georgievich. "Properties of the nucleus of an atom." Interactive science, no. 3 (89) (April 27, 2024): 64–68. http://dx.doi.org/10.21661/r-561878.

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Анотація:

Annotation The properties of the atomic nucleus were studied, in particular the weight of quarks and the energy of gluons were calculated. The nuclear potential and quark mass were calculated from the kinetic energy and momentum. This is determined using integers on which the mass of quarks and the energy of gluons depend. The mass of quarks is approximately known, and a dependence on integer numbers of the quark mass is selected that is close to the experimental value. This allows us to more accurately determine the mass of quarks that satisfy the kinetic energy of the quarks and their momentum. The energy of the atomic nucleus and the energy of the atom are determined using STR formulas at imaginary speed.

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15

Khunjua, Tamaz, Konstantin Klimenko, and Roman Zhokhov. "Dense quark matter with chiral and isospin imbalance: NJL-model consideration." EPJ Web of Conferences 191 (2018): 05015. http://dx.doi.org/10.1051/epjconf/201819105015.

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Анотація:

Isospin asymmetry is the well-known property of dense quark matter, which exists in the compact stars and is produced in heavy ion collisions. On the other hand, the chiral imbalance between left- and right- handed quarks is another highly anticipated phenomenon that could occur in the dense quark matter. To investigate quark matter under these conditions, we take into account baryon – μB, isospin – μI and chiral isospin – μI5 chemical potentials and study QCD phase portrait using NJL4 model generalized to two massive quarks that could condense into the pion condensation. We have shown that the chiral isospin chemical potential μI5 generates pion condensation in isospin asymmetric quark matter. Also, we have investigated discrete symmetry (duality) between chiral and pion condensates in the case of massless quarks, which stay relatively instructive even if the quarks have bare mass. To describe hot dense quark matter, in addition to the above-mentioned chemical potentials, we introduce non-zero temperatures into consideration.

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16

BAUNACK, SEBASTIAN. "ASYMMETRIES IN POLARIZED ELECTRON SCATTERING AND THE STRANGENESS CONTENT OF THE NUCLEON." Modern Physics Letters A 24, no. 11n13 (April 30, 2009): 881–86. http://dx.doi.org/10.1142/s021773230900022x.

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In the viewpoint of QCD, the nucleon is made up of constituent quarks, sea quarks and gluons. Concerning the quark sea, also strange quarks can contribute to the nucleon properties. Parity violating electron scattering offers a tool to investigate the strange quark contribution to the nucleon form factors. The measurements of different experiments are discussed and the recent results from the A4 collaboration at MAMI is presented. Altogether the existing data allow to give constraints on the strangeness contribution.

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17

Francis, Anthony, Renwick J. Hudspith, Randy Lewis, and Kim Maltman. "More on heavy tetraquarks in lattice QCD at almost physical pion mass." EPJ Web of Conferences 175 (2018): 05023. http://dx.doi.org/10.1051/epjconf/201817505023.

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Анотація:

We report on our progress in studying exotic, heavy tetraquark states, qq′ Q̅Q̅′. Using publicly available dynamical nf = 2 + 1 Wilson-Clover gauge configurations, generated by the PACS-CS collaboration, with pion masses ≃ 164, 299 and 415 MeV, we extend our previous analysis to heavy quark components containing heavier than physical bottom quarks Q̅Q̅′ = b̅′b̅′ or Q̅Q̅′ = b̅b̅′, charm and bottom quarks c̅b̅ and also only charm quarks c̅ c̅. Throughout we employ NRQCD and relativistic heavy quarks for the heavier than bottom, bottom and charm quarks. Using our previously established diquark-antidiquark and meson-meson operator basis we comment in particular on the dependence of the binding energy on the mass of the heavy quark component Q̅Q̅, with heavy quarks ranging from mQ = 0:85… 6.3 · mb. In the heavy flavor non-degenerate case, Q̅Q̅′, and especially for the tetraquark channel udc̅d̅, we extend our work to utilize a 3 × 3 GEVP to study the ground and threshold states thereby enabling a clear identification of possible binding. Finally, we present initial work on the Q̅Q̅′ = c̅c̅ system where a much larger operator basis is available in comparison to flavor combinations with NRQCD quarks.

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18

MAO, YAXIAN, WENCHANG XIANG, and DAICUI ZHOU. "CHARM QUARK ENERGY LOSS IN DENSE MATTER WITHIN THE LIGHT-CONE PATH INTEGRAL APPROACH." International Journal of Modern Physics E 16, no. 07n08 (August 2007): 2130–36. http://dx.doi.org/10.1142/s021830130700757x.

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Анотація:

The energy loss of heavy quarks traversing color dense matter is calculated with an analytical formula derived within the light-cone path integral (LCPI) approach. We find that the energy loss mechanism is dominated by gluon radiation and induces a suppression pattern of charm quark different from the suppression of light quarks. We find also that this radiative energy-loss is proportional to L2 for energetic quarks, but changes to a L dependance with decreasing quark energy, where L is the length of the traversed medium.

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19

Oka, Makoto. "Spectroscopy of heavy quark hadrons." International Journal of Modern Physics E 23, no. 07 (July 2014): 1461007. http://dx.doi.org/10.1142/s0218301314610072.

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Анотація:

Heavy quarks play special roles in the hadron spectroscopy. Some distinct features of heavy quark dynamics and their significance in the P-wave baryons with a single heavy quark are discussed. We also explore a new color configuration in exotic tetra-quark mesons with two heavy quarks. Finally, possibility of bound states of a charmed baryon with a nucleon and nuclei are examined.

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20

BEDNYAKOV, V. A. "ON LEADING CHARMED MESON PRODUCTION IN π–NUCLEON INTERACTIONS". Modern Physics Letters A 10, № 01 (10 січня 1995): 61–65. http://dx.doi.org/10.1142/s0217732395000077.

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Анотація:

It is shown that the D-meson, whose light quark is the initial-pion valence quark and whose charmed quark is produced in annihilation of valence quarks and has got a large enough momentum, is really a leading meson in reactions like π−p → DX. If such annihilation of valence quarks from initial hadrons is impossible there must be no distinct leading effect.

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21

LAI, XIAOYU, and RENXIN XU. "QUARK-CLUSTER STARS: THE STRUCTURE." International Journal of Modern Physics: Conference Series 23 (January 2013): 213–22. http://dx.doi.org/10.1142/s2010194513011331.

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Анотація:

The nature of pulsar-like compact stars is still in controversy although the first pulsar was found more than 40 years ago. Generally speaking, conventional neutron stars and non-mainstream quark stars are two types of models to describe the inner structure of pulsars, with the former composed mainly of hadrons and the latter of a peculiar kind of matter whose state equation should be understood in the level of quarks rather than hadrons. To construct a more realistic model from both theoretical and observational points of view, we conjecture that pulsars could be "quark-cluster stars" which are composed of quark-clusters with almost equal numbers of up, down and strange quarks. Clustering quark matter could be the result of strong coupling between quarks inside realistic compact stars. The lightest quark clusters could be of H-dibaryons, while quark clusters could also be heavier with more quarks. Being essentially related to the non-perturbative quantum-chromo dynamics (QCD), the state of supra-nuclear condensed matter is really difficult to obtain strictly by only theoretical QCD-calculations, and we expect, nevertheless, that astrophysical observations could help us to have a final solution.

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22

DAS, C. R., C. D. FROGGATT, L. V. LAPERASHVILI, and H. B. NIELSEN. "NEW BOUND STATES OF HEAVY QUARKS AT LHC AND TEVATRON." International Journal of Modern Physics A 26, no. 15 (June 20, 2011): 2503–21. http://dx.doi.org/10.1142/s0217751x11053420.

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Анотація:

The present paper is based on the assumption that heavy quarks bound states exist in the Standard Model (SM). Considering New Bound States (NBS) of top–antitop quarks (named T-balls) we have shown that: (1) there exists the scalar 1S-bound state of [Formula: see text]; (2) the forces which bind the top-quarks are very strong and almost completely compensate the mass of the twelve top–antitop-quarks in the scalar NBS; (3) such strong forces are produced by the Higgs–top-quarks interaction with a large value of the top-quark Yukawa coupling constant gt≃1. Theory also predicts the existence of the NBS [Formula: see text], which is a color triplet and a fermion similar to the t'-quark of the fourth generation. We have also considered the "b-quark-replaced" NBS, estimated the masses of the lightest fermionic NBS: M NBS ≳300 GeV , and discussed the larger masses of T-balls. We have developed a theory of the scalar T-ball's condensate and predicted the existence of three SM phases. Searching for heavy quark bound states at the Tevatron and LHC is discussed. We have constructed the possible form-factors of T-balls, and estimated the charge multiplicity coming from the T-ball's decays.

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23

MATUTE, ERNESTO A. "ELECTROWEAK QUARK–LEPTON SYMMETRY AND WEAK TOPOLOGICAL-CHARGE CONFINEMENT IN THE STANDARD MODEL WITH DIRAC NEUTRINOS." International Journal of Modern Physics A 22, no. 21 (August 20, 2007): 3669–91. http://dx.doi.org/10.1142/s0217751x0703683x.

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Анотація:

The standard electroweak model with Dirac neutrinos is extended by way of the principles of electroweak quark–lepton symmetry and weak topological-charge confinement to account for quark–lepton charge relations which, if not accidental, are indicative of charge structures. A mixing in quarks and leptons of underlying integer local charges with integer weak topological charges associated with an additive group Z3, fixed by the anomaly cancellation requirement, is discussed. It is found that the electroweak difference between topological quarks and leptons is the nonequivalence between the topological vacua of their weak field configurations, produced by a four-instanton which carries the topological charge, induces the universal fractional piece of charge distinguishing quarks from leptons, and breaks the underlying symmetry. The constituent quarks of the standard model appear as coming from topological quarks, via the weak four-instanton event. Dual transitions occur for leptons. It is shown that several other fundamental problems left open in the standard electroweak model with Dirac neutrinos are solved: the one-to-one correspondence between quark and lepton flavors, the existence of three generations, the conservation and ungauging of B-L, the electric charge quantization, and the confinement of fractional electric charges.

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24

Afonin, S. S., and I. V. Pusenkov. "Note on universal description of heavy and light mesons." Modern Physics Letters A 29, no. 35 (November 17, 2014): 1450193. http://dx.doi.org/10.1142/s0217732314501934.

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Анотація:

The experimental spectrum of excited S-wave vector mesons with hidden quark flavor reveals a remarkable property: For all flavors, it is approximately linear in mass squared, [Formula: see text], n is the radial quantum number. We draw attention to the fact that such a universal behavior for any quark mass cannot be obtained in a natural way within the usual semirelativistic potential and string-like models — if the Regge-like behavior is reproduced for the mesons composed of the light quarks, the trajectories become essentially nonlinear for the heavy-quark sector. In reality, however, the linearity for the heavy mesons appears to be even better than for the light ones. In addition, the slope a is quite different for different quark flavors. This difference is difficult to understand within the QCD string approach since the slope measures the interaction strength among quarks. We propose a simple way for reparametrization of the vector spectrum in terms of quark masses and universal slope and intercept. Our model-independent analysis suggests that the quarks of any mass should be regarded as static sources inside mesons while the interaction between quarks is substantially relativistic.

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25

BALL, R. D. "MESONS, SKYRMIONS AND BARYONS." International Journal of Modern Physics A 05, no. 23 (December 10, 1990): 4391–426. http://dx.doi.org/10.1142/s0217751x90001847.

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Анотація:

We review the construction of low energy effective actions for QCD expressed in terms of mesons and baryons rather than quarks and gluons. The mesons consist of quark-antiquark pairs bound by effective gluon exchange, while the baryons contain three valence quarks, also bound by effective gluon exchange, but enveloped in a meson cloud (the “sea quarks”), which may take the form of a chiral soliton. Such a “chiral quark soliton model” offers a unified approach to the various superficially dissimilar models of baryons currently popular, in particular constituent quark models, chiral bags, and Skyrmions, permitting an objective assessment of which is likely to be the most useful for a given physical problem.

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26

HEINZ, U., K. S. LEE, and M. J. RHOADES-BROWN. "$s-\bar{s}$ SEPARATION DURING HADRONIZATION OF A QUARK-GLUON PLASMA." Modern Physics Letters A 02, no. 03 (March 1987): 153–58. http://dx.doi.org/10.1142/s0217732387000197.

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Анотація:

We present the equilibrium phase diagram for hadronic and quark matter containing strange particles and show quantitatively that at finite baryon density hadronization of quark-gluon plasma proceeds through a mixed phase in which [Formula: see text]-quarks hadronize first (as K+ and K0 mesons) and s-quarks get enriched in the plasma subphase.

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27

GERASYUTA, S. M., and E. E. MATSKEVICH. "NONSTRANGE BARYONIA." International Journal of Modern Physics E 20, no. 06 (June 2011): 1419–36. http://dx.doi.org/10.1142/s0218301311018502.

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Анотація:

The relativistic six-quark equations including the u, d quarks and antiquarks are found. The nonstrange baryonia [Formula: see text] are constructed without the mixing of the quarks and antiquarks. The relativistic six-quark amplitudes of the baryonia are calculated. The poles of these amplitudes determine the masses of baryonia. 16 masses of baryonia are predicted.

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28

Giammanco, Andrea. "Single Top as Window on Heavy Quarks and Other New Physics." Advances in High Energy Physics 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/848491.

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Анотація:

This paper discusses what the study of the electroweak production of single top quarks can tell us about additional quark generations, and how to distinguish the new quarks hypothesis from other kinds of new physics. We also suggest some new studies that become possible for the first time thanks to the large statistics of single top quarks produced at the LHC.

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29

Pitt, Michael. "Diffractive and Photon-Induced Production of Top Quark." Universe 9, no. 11 (November 16, 2023): 483. http://dx.doi.org/10.3390/universe9110483.

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Анотація:

The top quark plays a central role in particle physics, as many experiments at the Large Hadron Collider scrutinize its properties within the Standard Model. Although most of the measurements of the top quarks today concentrate on production modes initiated by quarks or gluons, this review will highlight the lesser-explored modes initiated by pomerons or photons. It aims to provide an in-depth look into both the phenomenological studies and the existing experimental measurements, emphasizing the necessity of exploring the diffractive and photon-induced production of top quarks to enhance the accuracy of top-quark measurements.

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30

BATRA, M., та A. UPADHYAY. "DETAILED BALANCE AND SPIN CONTENT OF Λ USING STATISTICAL MODEL". International Journal of Modern Physics A 28, № 15 (16 червня 2013): 1350062. http://dx.doi.org/10.1142/s0217751x13500620.

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Анотація:

The spin structure of lambda has its special importance in analyzing the spin content of other hadrons. Assuming hadrons as a cluster of quarks and gluons (generally referred as valence and sea), statistical approach has been applied to study spin distribution of lambda among quarks. We apply the principle of detailed balance to calculate the probability of various quark–gluon Fock states and check the impact of SU(3) breaking on these probabilities particularly in sea for the Fock states containing strange quark. The flavor probability when multiplied by spin and color multiplicities of these quark–gluon Fock states results in estimating the individual contributions from valence and sea. We conclude that breaking in symmetry significantly affects the polarization of quarks inside the hyperons.

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31

CARIMALO, C. "QUARK MASS EFFECTS IN $\psi\to B\bar B$ DECAYS." International Journal of Modern Physics A 02, no. 01 (February 1987): 249–64. http://dx.doi.org/10.1142/s0217751x87000107.

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Анотація:

It is emphasized that since intermediate distances, in a range lying between confinement and asymptotic freedom, are probed in ψ decays, the quarks that constitute the hadrons produced in these decays should be considered as "constituent quarks" rather than "current quarks", as chiral-symmetry breaking effects should probably be already efficient in that range. In the case of ψ decays into baryon-antibaryon pairs, it is shown that the resulting quark mass effects may be important, especially when studying the angular distributions of the baryons emitted. Agreement with experimental data is found for these distributions, using a very simple nonrelativistic static quark model where each constituent quark in a baryon is assumed to have an effective mass of about a third of the baryon mass.

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32

Boldov, I. A. "Geometry of elementary particles." Mathematical structures and modeling, no. 4 (2022): 5–21. http://dx.doi.org/10.24147/2222-8772.2022.4.5-21.

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Анотація:

Based on the assumption that there is no direct causal relationship between the defect in the mass of atomic nuclei and the forces holding the nucleons in the nucleus [1], the hypothesis is put forward that the quarks are nucleons with whole Coulomb and other (baryon, lepton) charges. Based on the conclusions obtained by the author [1] that there is no fundamental prohibition on the use of approaches and concepts of the macrocosm in the physics of the microcosm, and that the mass in the space of our Universe is equivalent to a three-dimensional volume, a comparison of the geometry of elementary particles and quarks to regular (semi-regular) polyhedra is proposed. It is assumed that the mass of a particle is determined by the volume of the corresponding polyhedron-a quark (or the sum of the volumes of quarks, with a discrete (quantized) edge length of the polyhedron. An assumption is made about the possibility of oscillation not only of neutrinos, but also of oscillations of other charged leptons (quarks) occurring during particle decays, with non-preservation of symmetry groups of quarks-polyhedra, as well as about the possibility of intra-group oscillation of pairs of identical quarks. It is suggested that during the processes of creation or decay of particles, quark-antiquark pairs (𝑞𝑞¯) are always present in space due to ¡¡boiling vacuum¿¿. Taking into account the above, the formulas of particle reactions are given in a strict mathematical form. The sums of quarks (leptons) before the reaction and after are equal, taking into account the oscillations. Computer modeling is carried out - comparison of the masses of elementary particles to the sums of polyhedra for mesons, baryons, tetraquarks, pentaquarks and hexaquarks. An attempt is made to systematize the entire list of elementary particles in ¡¡Tables of quark combinations¿¿, similar to the Table of D.I. Mendeleev for chemical elements. In the proposed tables, all elementary particles of a given set of quarks and of different masses are assumed in each cell. The shape of nucleons with external quarks-cubes obtained as a result of the juxtaposition of quarks-polyhedra gives reason to assume the spatial anisotropy of the so-called ”nuclear forces” in the form of six orthogonal directions of interaction.

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33

TERAZAWA, HIDEZUMI. "TRIPLICITY OF HADRONS, QUARKS AND SUBQUARKS." Modern Physics Letters A 05, no. 13 (May 30, 1990): 1031–39. http://dx.doi.org/10.1142/s0217732390001153.

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Анотація:

Triplicity of hadrons, quarks and subquarks asserting that a certain physical quantity such as the weak current can be taken equally well as a composite operator of hadrons, or of quarks, or of subquarks is proposed. Among others, the weak mixing angle, the quark mixing matrix and the mass sum rules for quarks and leptons are revisited, reinterpreted and discussed in detail in triplicity.

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34

Hamad, Ayman, Salem Abdulkarim, and Farag Hamad. "First Order Harmonic Flow of Heavy Quarks using a Hybrid Transport Model." Scholars Journal of Physics, Mathematics and Statistics 10, no. 2 (February 3, 2023): 49–52. http://dx.doi.org/10.36347/sjpms.2023.v10i02.001.

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We report the investigation of the first order flow of charmed quarks in gold-to-gold collision at the energy near to the speed of the light using A Multi-Phase Transport (AMPT) model. We have used the AMPT string melting version known as partonic interactions option. In this study, we investigated the directed flow v1 of the charmed quark D0 as a function of rapidity. The model predicts the correct sign for D0v1, but the size of the predicted directed flow signal is too small by about an order of magnitude comparing to the real data from the STAR collaboration analysis. The AMPT model shows that the charm quark v1 magnitude is larger than that of the light quarks at large rapidity. This indicates that the charm quarks can retain more information from initial condition than the light quarks.

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35

Pan, Ying-Hua, and Wei-Ning Zhang. "Chemical Evolution of Strongly Interacting Quark-Gluon Plasma." Advances in High Energy Physics 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/952607.

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Анотація:

At very initial stage of relativistic heavy ion collisions a wave of quark-gluon matter is produced from the break-up of the strong color electric field and then thermalizes at a short time scale (~1 fm/c). However, the quark-gluon plasma (QGP) system is far out of chemical equilibrium, especially for the heavy quarks which are supposed to reach chemical equilibrium much late. In this paper a continuing quark production picture for strongly interacting QGP system is derived, using the quark number susceptibilities and the equation of state; both of them are from the results calculated by the Wuppertal-Budapest lattice QCD collaboration. We find that the densities of light quarks increase by 75% from the temperatureT=400 MeV toT=150 MeV, while the density of strange quark annihilates by 18% in the temperature region. We also offer a discussion on how this late production of quarks affects the final charge-charge correlations.

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36

Mykhaylova, Valeriya. "Charm quark fugacity in hot QCD." EPJ Web of Conferences 274 (2022): 05006. http://dx.doi.org/10.1051/epjconf/202227405006.

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Анотація:

We study the fugacity of charm quarks in hot QCD from the quasiparticle perspective. The system is described in terms of dynamical quarks and gluons dressed by the effective temperature-dependent masses which link the thermodynamics of the model to the lattice QCD data for Nf = 2 + 1. We insert the charm quarks „by hand” and investigate how their scatterings with the quasiparticles affect the charm quark fugacity in a viscous medium expanding in all spatial dimensions and in the perfect fluid propagating longitudinally. We find that the charm quark fugacity strongly depends on the evolution of the deconfined matter at early stages while behaving universally close to the QCD crossover.

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37

Zweig, George. "Concrete quarks." International Journal of Modern Physics A 30, no. 01 (January 9, 2015): 1430073. http://dx.doi.org/10.1142/s0217751x14300737.

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Анотація:

A short history of the physics of strongly interacting particles is presented. Events leading to the discovery, and eventual acceptance, of concrete quarks are described. (Other aspects of quark history are given in Refs. 1 and 2.)

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38

Gomes, Frederico F., Bruna C. Folador, Dimiter Hadjimichef, and Daniel T. da Silva. "A Heavy-Light Quark Potential." International Journal of Modern Physics: Conference Series 45 (January 2017): 1760054. http://dx.doi.org/10.1142/s2010194517600540.

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Анотація:

In many studies of meson-baryon interactions with short one gluon exchange potential (OGEP), usually a full non-relativistic reduction, at the quark level Hamiltonian, is performed. In systems like [Formula: see text], light and heavy quarks are present, which in principle would require only a partial non-relativistic reduction. We shal start from a JKJ relativistic quark Hamiltonian and apply a partial non-relativistic reduction in order to obtain a OGEP between heavy and light quarks (heavy-light quark potential).

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39

RAJPOOT, SUBHASH. "ANOMALY FREEDOM THROUGH LEPTO-QUARK MATTER." Modern Physics Letters A 05, no. 03 (January 30, 1990): 189–94. http://dx.doi.org/10.1142/s0217732390000238.

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Анотація:

Lepto-quark matter represents new fermionic matter that carries quark as well as lepton numbers. An extension of the standard model with three families of conventional quarks and leptons is presented in which freedom from anomalies is secured through the presence of lepto-quark matter representations. The gauge symmetry of the model is SU(2)L×U(1)q×U(1)l where U(1)q and U(1)l refer to distinct hypercharge sources for the quarks and the leptons.

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40

RODIONOV, E. N., A. W. THOMAS, and J. T. LONDERGAN. "CHARGE ASYMMETRY OF PARTON DISTRIBUTIONS." Modern Physics Letters A 09, no. 19 (June 21, 1994): 1799–806. http://dx.doi.org/10.1142/s0217732394001659.

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Анотація:

We calculate the valence distribution of down quarks in the proton and up quarks in the neutron (the ‘minority’ quark distributions), taking into consideration the major sources of charge symmetry violation, including the effect of the mass difference of the u and d quarks on the bag wave function, and the masses of the intermediate diquark states. The relative difference of the distributions can be as large as 10% for intermediate values of Bjorken x.

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41

Xu, Shu-Sheng, Yan Yan, Zhu-Fang Cui, and Hong-Shi Zong. "2+1 flavors QCD equation of state at zero temperature within Dyson–Schwinger equations." International Journal of Modern Physics A 30, no. 36 (December 30, 2015): 1550217. http://dx.doi.org/10.1142/s0217751x15502176.

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Анотація:

Within the framework of Dyson–Schwinger equations (DSEs), we discuss the equation of state (EOS) and quark number densities of 2+1 flavors, that is to say, [Formula: see text], [Formula: see text], and [Formula: see text] quarks. The chemical equilibrium and electric charge neutrality conditions are used to constrain the chemical potential of different quarks. The EOS in the cases of 2 flavors and 2+1 flavors are discussed, and the quark number densities, the pressure, and energy density per baryon are also studied. The results show that there is a critical chemical potential for each flavor of quark, at which the quark number density turns to nonzero from 0; and furthermore, the system with 2+1 flavors of quarks is more stable than that with 2 flavors in the system. These discussions may provide some useful information to some research fields, such as the studies related to the QCD phase transitions or compact stars.

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42

Truten, Ivan V., and Alexander Yu Korchin. "Energy correlation of bottom quarks from decays of top quarks in electron–positron annihilation." Journal of Physics G: Nuclear and Particle Physics 49, no. 4 (February 24, 2022): 045003. http://dx.doi.org/10.1088/1361-6471/ac4e60.

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Анотація:

Abstract Joint energy distribution of the bottom quark and antiquark from decays of the top quark and antiquark produced in the reaction e + e − → t t ¯ is studied. Main emphasis is put on CP-violation effects in the interaction of the photon and Z boson with the top quarks. Energy asymmetries of b and b ¯ quarks, which give access to the CP-violating terms, are considered. To estimate the magnitude of these asymmetries, the CP-violating γtt and Ztt couplings are calculated in one-loop model with exchange of the Higgs boson with the mass of 125 GeV. Interaction of this boson with the top quarks is assumed to include scalar and pseudoscalar couplings. Values of these couplings are constrained from the recent CMS analysis. Energy dependence of the asymmetries of b and b ¯ quarks is calculated up to s = 1.2 TeV and some interesting features of their behavior are observed. These observables can be of interest for future studies at electron–positron colliders CLIC and ILC.

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43

Hansson, J. "A simple explanation of the nonappearance of physical gluons and quarks." Canadian Journal of Physics 80, no. 9 (September 1, 2002): 1093–97. http://dx.doi.org/10.1139/p02-034.

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Анотація:

We show that the nonappearance of gluons and quarks as physical particles is a rigorous and automatic result of the full, i.e., nonperturbative, nonabelian nature of the color interaction in quantum chromodynamics (QCD). This makes it, in general, impossible to describe the color field as a collection of elementary quanta (gluons). Neither can a quark be an elementary quantum of the quark field, as the color field of which it is the source is itself a source, making isolated noninteracting quarks, crucial for a physical particle interpretation, impossible. In geometrical language, the impossibility of quarks and gluons as physical elementary particles arises due to the fact that the color YangMills space does not have a constant trivial curvature. In QCD, the particles "gluons" and "quarks" are merely artifacts of an approximation method (the perturbative expansion) and are simply absent in the exact theory. This also coincides with the empirical, experimental evidence. PACS Nos.: 12.38Aw, 03.70+k, 11.15-q

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44

ROBSON, B. A. "A GENERATION MODEL OF COMPOSITE LEPTONS AND QUARKS." International Journal of Modern Physics E 14, no. 08 (November 2005): 1151–69. http://dx.doi.org/10.1142/s0218301305003776.

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Анотація:

A new composite model for leptons and quarks is presented. The model treats leptons and quarks as composites of three kinds of spin-½ particles (rishons), which belong to a fundamental triplet representation of a flavor SU (3) symmetry. A super-strong color-type force binds rishons together to form colorless leptons or quarks. Quarks display a valence property, which corresponds to the quark color of the Standard Model. Leptons have no valence property and are inert with respect to the super-strong color interaction. Both the strong color force and the weak interaction of the Standard Model are residual interactions of the super-strong color force in the new model.

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45

HIDAKA, YOSHIMASA, and MASAKIYO KITAZAWA. "SPECTRUM OF SOFT MODE WITH THERMAL MASS OF QUARKS ABOVE CRITICAL TEMPERATURE." International Journal of Modern Physics E 16, no. 07n08 (August 2007): 2394–99. http://dx.doi.org/10.1142/s0218301307007994.

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Анотація:

We study effects of a thermal-quark mass and Landau damping of quarks on the chiral phase transition and its soft modes at finite temperature. For this purpose we employ a simple model with the quark propagator obtained in the hard thermal loop approximation. We show that the chiral phase transition is second order even if quark have a finite thermal mass, and the thermal mass suppresses the chiral condensate. We argue that mesonic spectra have a large width due to scattering between gluons and quarks, and the van Hove singularity at threshold.1.

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46

Morimoto, Masatoshi, Yasuhiko Tsue, João da Providência, Constança Providência, and Masatoshi Yamamura. "Spontaneous magnetization under a pseudovector interaction between quarks in high density quark matter." International Journal of Modern Physics E 27, no. 04 (April 2018): 1850028. http://dx.doi.org/10.1142/s0218301318500283.

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Анотація:

Spontaneous magnetization and magnetic susceptibility originated from the pseudovector-type four-point interaction between quarks are calculated in quark matter with zero temperature and finite quark chemical potential by using the two-flavor Nambu–Jona-Lasinio model. It is shown that both the chiral condensate and spin polarized condensate coexist in a narrow region of the quark chemical potential. And then, it is also shown that, in this narrow region, the spontaneous magnetization appears. Also, the magnetic susceptibility due to quarks with the positive energy is evaluated in the spin polarized phase.

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47

RHO, MANNQUE. "MASSIVE-QUARK BARYONS AS SKYRMIONS." Modern Physics Letters A 06, no. 23 (July 30, 1991): 2087–100. http://dx.doi.org/10.1142/s0217732391002268.

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Анотація:

Massive-quark baryons containing one or more charm (c) or bottom (b) quarks are described as massive scalar doublet fields "wrapped" by the soliton of the light (up and down) flavors. The spin-isospin transmutation that takes place to make the trapped scalar behave like heavy-flavored quarks is analogous to what happens to a scalar doublet in the presence of a 't Hooft–Polyakov monopole. The Wess–Zumino term plays a pivotal role here. This model predicts spectra that resemble closely those of quark models. This feature is interpreted in terms of an induced gauge (or Berry) structure associated with "fast" and "slow" degrees of freedom corresponding, respectively, to the massive- and light-flavor quarks involved in the baryon structure.

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48

Juárez Wysozka, S. R., and P. Kielanowski. "Test of the fourth quark generation from the Cabibbo–Kobayashi–Maskawa matrix." International Journal of Modern Physics A 36, no. 16 (June 2, 2021): 2150110. http://dx.doi.org/10.1142/s0217751x21501104.

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Анотація:

The structure of the mixing matrix in the electroweak quark sector with four generations of quarks is investigated. We conclude that the area of the unitarity quadrangle is not a good choice as a possible measure of the CP violation. In search of new physics, we analyze how the existence of the fourth quark family may influence on the values of the Cabibbo–Kobayashi–Maskawa matrix and we show that one can test for the existence of the fourth generation using the Jarlskog invariants of the known quarks only. The analysis based on the measured unitary triangle exhibits some tension with the assumption of three quark generations. The measurement of the unitarity triangle obtained from the scalar product of the second row/column of the CKM matrix by the complex conjugate of third row/column can provide information about the existence of the fourth generation of quarks.

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49

Ma, Xin-Hua. "Consideration of Additive Quantum Numbers of Fermions and Their Conservations." Universe 7, no. 9 (August 27, 2021): 317. http://dx.doi.org/10.3390/universe7090317.

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Анотація:

Two new flavor quantum numbers D and U for down and up quarks, respectively, are introduced, and then quark quantum number H is proposed as the sum of the flavor quantum numbers of quarks. Moreover, lepton quark-like quantum number HL and finally fermion quantum number F are brought forward. Old and new additive quantum numbers are conserved at three different levels in weak interaction, and F builds up a clear relationship to the electric charge of fermions.

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50

YÉPEZ, TOCHTLI, A. AMOR, PETER O. HESS, A. SZCZEPANIAK, and O. CIVITARESE. "ANALYTIC SOLUTIONS OF QCD MOTIVATED HAMILTONIANS AT LOW ENERGY." International Journal of Modern Physics E 20, supp02 (December 2011): 192–99. http://dx.doi.org/10.1142/s0218301311040797.

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Анотація:

A model Hamiltonian, motivated by QCD, is investigated in order to study only the quark sector, then only the gluon sector and finally both together. Restricting to the pure quark sector and setting the mass of the quarks to zero, we find analytic solutions, involving two to three orbitals. Allowing the mass of the quarks to be different to zero, we find semi-analytic solutions involving an arbitrary number of orbitals. Afterwards, we indicate on how to incorporate gluons.

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