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1
Allport, P. P. « High energy neutrino scattering at low Q'2 ». Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376865.
Texte intégral
2
Re, Fiorentin Michele. « Understanding and predicting low-energy neutrino parameters with leptogenesis ». Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/400882/.
Texte intégralRésumé :
In this work, we address two major problems of the Standard Model of particle physics: the baryon asymmetry of the Universe and neutrino masses and mixing. A strict link between these two aspects can be established by the seesaw mechanism and leptogenesis. This connection can be fruitfully exploited to gain information on neutrino parameters. To this aim, we first introduce the type-I seesaw mechanism and leptogenesis, moving then to the strong thermal leptogenesis scenario. Here a large pre-existing asymmetry is efficiently erased by leptogenesis, and an analytical lower bound on the absolute neutrino mass scale can be derived. We then consider SO(10)-inspired leptogenesis, in which a set of conditions kindred to those realised in SO(10) Grand Unification Theories is imposed on the seesaw setup. A rigorous analytical study of this scenario is performed, allowing us to obtain analytical explanations of the numerous predictions on neutrino parameters. SO(10)-inspired and strong thermal SO(10)-inspired leptogenesis appear then to represent a very interesting scenario, rich of definite predictions on neutrino parameters that will be in the reach of forthcoming experiments. Finally, we examine the supersymmetric extension of SO(10)-inspired leptogenesis, analysing how the constraints on neutrino parameters change. The lower bound imposed by thermal leptogenesis on the reheating temperature is carefully studied, in light of the gravitino problem. We conclude that the thermal leptogenesis scenario represents an intriguing and viable mechanism also in the supersymmetric framework.
3
Li, Tracey Chuiyee. « Phenomenology of a low-energy neutrino factory and related experiments ». Thesis, Durham University, 2010. http://etheses.dur.ac.uk/613/.
Texte intégralRésumé :
The discovery of neutrino oscillations is one of the most important in the recent history of particle physics, being the first evidence of physics beyond the Standard Model. We describe the theoretical framework of the neutrino oscillation model, motivate the necessity for a new generation of neutrino oscillation experiments and study the phenomenological factors which influence the design of these experiments. We perform the first detailed study of a European super-beam setup using the CERN to Pyhasalmi baseline of 2285 km, analysing the physics reach of this setup with a 100 kiloton liquid argon detector and comparing its performance to that of a 50 kiloton liquid scintillator detector and a 440 kiloton water Cerenkov detector. The liquid argon and liquid scintillator detectors are found to perform best, providing sensitivity to θ₁₃, δ and the mass hierarchy for sin²2θ₁₃ > 10⁻². A potential successor to super-beam experiments is a neutrino factory. We study a low-energy neutrino factory, a setup which has so far not been analysed in any detail, performing optimisation studies and an analysis of its sensitivity to oscillation parameters and non-standard matter interactions. We show that for sin²2θ₁₃ > 4x10⁻³, a low-energy neutrino factory using a 20 kiloton totally active scintillating detector has 100% CP coverage for hierarchy sensitivity and θ₁₃ discovery, and has greater sensitivity to CP violation than the high-energy neutrino factory. We consider the novel concept of including the 'platinum channels' in addition to the 'golden channels', showing that this is a powerful way of resolving the degeneracies between the oscillation and non-standard parameters. This enhances the sensitivity, such that the low-energy neutrino factory can put upper bounds ≳10⁻² on the non-standard interaction parameters ε_eμ and ε_eτ.
4
Marzola, Luca. « On leptogenesis, flavour effects and the low energy neutrino parameters ». Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/346819/.
Texte intégralRésumé :
Contemporary physics is testing the boundaries of one of its existent paradigms, the Standard Model of Particle Physics. In recent years many attempts have been made in order to overcome the difficulties arising within this well known framework. Along with the effort made on the experimental side, for example the search for the Higgs boson at the Large Hadron Collider, there is a present requirement for testable theoretical scenarios describing physics beyond the current paradigms. To this purpose we consider the type I Seesaw extension of the Standard Model, in which the neutrino mass puzzle is possibly solved and the baryon asymmetry of the Universe explained via Leptogenesis. After reviewing the basis of the Seesaw mechanism and its recent developments we present a rigorous investigation which confirms the validity of the adopted description. Encouraged by this success we then employ the interplay of light and heavy neutrino flavour e↵ects to address the problem of initial conditions in Leptogenesis. Our analysis identifies the ⌧ N2-dominated scenario as the only possible answer, proposing a well defined setup in which successful strong thermal Leptogenesis is achieved. Attracted by the properties of our solution we consequently investigate its compatibility with the SO(10)-inspired model of Leptogenesis. The result is indeed intriguing: the strong thermal solutions of the SO(10)-inspired model deliver sharp predictions on the lowenergy neutrino parameters that fall within the reach of future neutrino experiments,opening up the possibility of a full test of this attractive Leptogenesis scenario.
5
PICCIAU, EMMANUELE. « Low-energy signatures in DarkSide-50 experiment and neutrino scattering processes ». Doctoral thesis, Università degli Studi di Cagliari, 2022. http://hdl.handle.net/11584/327520.
Texte intégralRésumé :
Dark matter is one of the greatest unsolved mysteries in cosmology nowadays.
About 80% of the gravitating matter in the Universe is non-luminous, and its
nature and distribution are for the most part unknown. Many experiments
around the world and in space are trying to discover dark matter interactions
and properties. Among them, the DarkSide project aims to see dark matter
signatures inside of time projection chamber filled with liquid argon. In
order to reach such a goal, the detector features along with the background
must be studied and well understood. This thesis presents the so-called
single-electron background of DarkSide-50 experiment, with the perspective
of informing the community on the backgrounds which may affect future
experiments, especially those looking for low-mass dark matter particles.
Another important and irreducible background to be considered in the future
regards the coherent neutrino-nucleus scattering in the detector. This process
is supposed to mimic in a very similar way the dark matter interaction, making
its discovery even harder. For this reason, it is crucial to increase the knowledge
of the electroweak and nuclear parameters which are involved in the neutrino
scattering process. In this thesis, several phenomenological studies regarding
the recent discovery of coherent neutrino-nucleus scattering are presented,
along with the determination of quantities accessible through this channel.
6
O'Keeffe, Helen Mary. « Low energy background in the NCD phase of the Sudbury Neutrino Observatory ». Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:b53c04b1-5dba-4cfb-98ec-c0d8b87fb58b.
Texte intégralRésumé :
The Sudbury Neutrino Observatory (SNO) was a 1 kilotonne heavy water Č{C}erenkov detector. Evidence for flavour changing neutrino oscillations was found by comparing the rate of Charged Current interactions with that of Neutral Current (NC) interactions. This thesis is concerned with the accurate determination of the NC flux in the Neutral Current Detector (NCD) phase of SNO. The measurement and understanding of radioactive backgrounds arising from decays of naturally occurring $^{232}$Th and $^{238}$U chain nuclei is crucial. This is because their daughter nuclei can produce neutrons via photodisintegration of deuterium. These would be indistinguishable from those produced by NC neutrino interactions. As the probability of neutron production was dependent upon the nature and location of activity, each contribution had to be determined separately. Of particular concern were $^{232}$Th and $^{238}$U in the D$_2$O and Neutral Current Detectors (NCDs). A maximum likelihood method was developed that exploited differences in the event isotropy and radial profile of each event class. These results were in agreement with water assay results and pre-deployment radioassays of the NCDs. An independent measurement of the $^{232}$Th content in the D$_2$O and H$_2$O was made by regularly assaying the water using filters loaded with hydrous titanium oxide. The concentration of $^{232}$Th in the water was determined by coincidence counting of the final assay sample. A new counter system was designed and built and the calibration and use of this system are presented. Two areas of increased activity were discovered on two of the NCDs deployed in the detector which would have prevented an accurate measurement of the NC flux. A method was devised to determine the composition and activity of one of these hotspots. The results were in good agreement with two independent methods and the uncertainty on the NC flux was reduced from $>7$% to $<1$%. The total number of neutrons produced per day by photodisintegration for $^{232}$Th and $^{238}$U in the D$_2$O and NCDs was measured to be $0.66^{+0.08}_{-0.07}$. This was significantly less than the expected 12.6 NC neutrino interactions per day. In the third phase, two independent data streams existed: PMT and NCD. A Monte Carlo study was undertaken to determine whether an accurate measure of the NC flux could be obtained using only PMT data. Results showed that no improvement could be made upon results from previous phases and the best measurement of the NC flux in the final phase would be made using PMT and NCD data.
7
Manecki, Szymon M. « Annual Modulation Measurement of the Low Energy Solar Neutrino Flux with the Borexino Detector ». Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23250.
Texte intégralRésumé :
This work reports a first attempt to measure the solar neutrino annualflux modulation due to Earth\'s elliptical orbit with the Borexino detector. Borexino is a real-time calorimetric detector for low energy neutrino spectroscopy located in the underground laboratory of Gran Sasso, Italy. The experiment\'s main focus is the direct measurement of the 7Be solar neutrino flux of all flavors via neutrino-electron scattering in an ultra-pure scintillation liquid. The original goal of this work was to quantify sensitivity of the Borexino detector to a 7% peak-to-peak signal variation over the course of a year and study background stability. A Monte-Carlo simulated sample of the expected variation was prepared in two phases of data acquisition, Phase I that spans from May-2007 to May-2010 and Phase II from October-2011 to September-2012. The data was then fitted in the time domain with a sinusoidal function and analyzed with the Lomb-Scargle fast Fourier transformation in the search for significant periodicities between periods of 0.5 and 1.5 years. The search was performed in the energy window dominated by 7Be, [210; 760] keV, and 60-day bins in the case of the fit and 10-bins for the Lomb-Scargle scan. This work also contains study of the post-purification data of Phase II beyond September-2012 with a prediction for the future sensitivity and justification of the achieved background levels.
Ph. D.
8
Bilmis, Selcuk. « Study On Non Standard Interaction Of Neutrino And Unparticle Physics With Neutrino-electron Scattering Data At Low Energy In Texono Experiment ». Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612495/index.pdf.
Texte intégralRésumé :
Neutrino-electron scatterings are purely leptonic processes with robust Standard Model (SM)
predictions. Their measurements can therefore provide constraints to physics beyond SM.
The &nue &minus
e&minus
data taken at the Kuo-Sheng Reactor Neutrino Laboratory were used to probe two sceneria: Non-Standard Neutrino Interactions (NSI) and Unparticle Physics. New constraints were placed to the NSI parameters (&epsilon
eL , &epsilon
eR ), (&epsilon
eL , &epsilon
eR ) and (&epsilon
eL , &epsilon
eR ) , as well as to the coupling constants for scalar (&lambda
0 ) and vector (&lambda
1 ) unparticles to the neutrinos and electrons.
9
Xu, Yu [Verfasser], Livia [Akademischer Betreuer] Ludhová et Achim [Akademischer Betreuer] Stahl. « Machine learning application in low energy liquid scintillator neutrino experiment / Yu Xu ; Livia Ludhová, Achim Stahl ». Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1226218601/34.
Texte intégral
10
Marta, Michele. « The 14N(p,γ)15O reaction studied at low and high beam energy ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-87464.
Texte intégralRésumé :
The CNO cycle consists of a set of nuclear reactions that convert hydrogen into helium and releases energy in stars. The cycle contributes less than 1% to our Sun's luminosity, but it is responsible for detectable neutrino fluxes that can bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision.
The 14N(p,γ)15O is the slowest reaction in the CNO cycle and estabilishes its rate. The experimental study has been performed both at the LUNA 400 kV accelerator deep underground in the Gran Sasso mountain in Italy and at a 3 MV Tandetron in the Helmholtz-Zentrum Dresden-Rossendorf. A proton beam was sent on solid TiN targets and the prompt photons were collected by a composite HPGe detector (at LUNA) or by up to four HPGe detectors (Dresden).
The obtained results improve the fit of the excitation function in the R-matrix framework, that is used to extrapolate the S-factor at the very low astrophysical energies. In addition, the strength of two resonances at Ep = 430 and 897 keV of the 15N(p,αγ)12C reaction were measured, improving the precision for hydrogen depth profiling.
11
Rountree, Steven Derek. « Science and Technology of a Low-Energy Solar Neutrino Spectrometer (LENS) and Development of the MiniLENS Underground Prototype ». Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/27803.
Texte intégralRésumé :
A real time low energy spectral measurement of the neutrinos coming from the Sun will give us a greater understanding of energy production in the Sun, and the mechanisms of neutrino mixing. We will, for the first time, measure the solar neutrino spectrum for all solar neutrinos <2MeV in particular pp, Be and CNO neutrinos, be able to compare the solar photon derived energy luminosity (Lï §) to the solar neutrino derived energy luminosity (Lï ®) independent of any solar model, explore dark energy with respect to mass varying neutrinos, and explore CNO abundances in the Sun. These measurements require new technology in Indium loaded scintillators and large scale detector designs, namely increased spatial resolution through a novel scintillation lattice. I will present the advances we are making to these fields at Virginia Tech as well as neutrino science and the physics of the LENS detector.Ph. D.
12
Funcke, Lena [Verfasser], et Georgi [Akademischer Betreuer] Dvali. « How gravity shapes the low-energy frontier of particle physics : neutrino masses and the domestic axion / Lena Funcke ; Betreuer : Georgi Dvali ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1196008752/34.
Texte intégral
13
Daub, Brian (Brian Hollenberg). « Low energy neutron-proton interactions ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76978.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 265-270).
There have been few measurements of cross sections for neutron-proton scattering and radiative capture below 1 MeV. Those measurements which do exist are at a small number of energies and are often inconsistent with theoretical models and with each other. We have conducted several experiments with the goal of obtaining improved data on these cross sections at the University of Kentucky (UKY) and the Los Alamos Neutron Science Center (LANSCE). Feasibility studies for measuring the low energy cross section for np radiative capture have been conducted at both UKY and LANSCE, culminating in a measurement of the cross section at 0.5, 0.9, 1.5, 2.0, and 2.5 MeV at UKY, using a plastic scintillator to detect recoiling deuterons and two BGO scintillators to detect the [gamma]-ray yields at 64.6° and 106.6°. We also performed measurements of the response of BC418 plastic scintillator to low energy protons during these studies, and conducted several additional measurements of the scintillator response at LANSCE and UKY, yielding very precise results from 100 keV to 3.6 MeV. The total cross section for np scattering was measured at UKY from 150 to 800 keV by neutron transmission, measuring the neutron yields in a liquid scintillator with various targets in the beam. The cross section was determined by taking ratios of neutron yields with and without the target, giving cross sections which are independent of detector efficiency and dead time. These results fill a significant gap in the available data below 500 keV.
by Brian Daub.
Ph.D.
14
Weiland, Cedric. « Effects of fermionic singlet neutrinos on high- and low-energy observables ». Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00922999.
Texte intégralRésumé :
In this doctoral thesis, we study both low- and high-energy observables related to massive neutrinos. Neutrino oscillations have provided indisputable evidence in favour of non-zero neutrino masses and mixings. However, the original formulation of the Standard Model cannot account for these observations, which calls for the introduction of new Physics. Among many possibilities, we focus here on the inverse seesaw, a neutrino mass generation mechanism in which the Standard Model is extended with fermionic gauge singlets. This model offers an attractive alternative to the usual seesaw realisations since it can potentially have natural Yukawa couplings (O(1)) while keeping the new Physics scale at energies within reach of the LHC. Among the many possible effects, this scenario can lead to deviations from lepton flavour universality. We have investigated these signatures and found that the ratios R_K and R_π provide new, additional constraints on the inverse seesaw. We have also considered the embedding of the inverse seesaw in supersymmetric models. This leads to increased rates for various lepton flavour violating processes, due to enhanced contributions from penguin diagrams mediated by the Higgs and Z bosons. Finally, we also found that the new invisible decay channels associated with the sterile neutrinos present in the supersymmetric inverse seesaw could significantly weaken the constraints on the mass and couplings of a light CP-odd Higgs boson.
15
Padilla, Eduardo A. « Characterization of fissile material using low energy neutron interrogation ». Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41299.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.Includes bibliographical references (p. 76).
The glaring need to develop methods for detecting and interdicting illicit nuclear trafficking has resulted in the exploration of various methods for active neutron interrogation, specifically for the presence of special nuclear material (SNM) in cargo containers. The proposed system aims to defeat the ability of terrorists to import SNM into the United States via maritime shipping, thus greatly reducing the possibility of a successful nuclear terrorist attack. The proposed system uses 60-100 keV neutrons, produced by the 7Li(p,n)7Be reaction in a linear accelerator and kinematically beamed into various targets. In the event that fissile material is present, highly energetic neutrons will be emitted from the fissioning of a nucleus and some of these neutrons will eventually radiate from the container. Inevitably, high energy photons will also radiate from the target due to the interactions of neutrons and host materials. Utilizing a neutron detection system that is able to discriminate low energy neutrons, high energy gamma rays and the high energy neutrons from fission enables the detection of fissile material in various containers. An increase in discriminated high energy neutron events during active neutron interrogation selectively indicates the presence of SNM, since neutron energies on the order of 1 MeV are required for the SNM-equivalent fissioning potential when incident upon U238 and other high-Z nuclei. Furthermore, neutrons with less than approximately 100 keV do not undergo nuclear processes such as (n,2n) and (n,n'), but rather lose their energy through kinematic collisions.
(cont.)Results obtained validate this proof-of-concept, in that observed high energy neutron events increase significantly in the presence of gram-quantities of SNM. Further, attempts made to shield the SNM from active interrogation do not defeat the proposed system's ability to identify the presence of SNM. With a fully-functional proof-of-concept, further work towards developing a complete and deployable prototype active neutron interrogation system will serve to augment the ability of the United States to detect, deter and interdict illicit nuclear trafficking.
by Eduardo A. Padilla.
S.M.
16
Pidopryhora, Yurii. « Testing the low energy theorem for spinless "proton-neutron" bremsstrahlung ». Ohio : Ohio University, 2003. http://www.ohiolink.edu/etd/view.cgi?ohiou1060029614.
Texte intégral
17
Habeck, Christian. « Experimental determination of the weak coupling constant ratio Gâ†A/Gâ†V in neutron decay ». Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364138.
Texte intégral
18
Schwarzenberg, Johannes von. « Very converted low-energy transitions in nuclei in the A = 180 - 190 region ». Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30894.
Texte intégral
19
Johnson, Erik D. Ph D. Massachusetts Institute of Technology. « Monte Carlo model of a low-energy neutron interrogation system for detecting fissile material ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41262.
Texte intégralRésumé :
Includes bibliographical references (p. 66-67).Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.
(cont.) Further MCNP simulations of the neutron source impinging on cargo containers suggest that this technique can respond, as expected, qualitatively differently to containers containing SNM from containers that do not. Containers that contain small amounts of fissile isotopes as in the case of a few grams of uranium-235 in a kilogram of depleted uranium will also respond to this method but much more weakly. The system as proposed is viable and further simulation and experimental work will elucidate the behavior of this system under a wide range of cargo environments.
The undeniable threat of nuclear terrorism presents an opportunity for innovation in developing active interrogation technology. The proposed system aims to detect the smuggling of special nuclear material (SNM) in maritime containers. Identifying the importation of SNM will be instrumental in protecting the American public from a nuclear terrorist attack made possible by the construction of a weapon with fissile material from abroad. The proposed system uses a directionally-biased beam of low-energy neutrons (60 - 100 keV) generated from a 7Li(p,n)7Be reaction run near threshold. These neutrons are directed towards a cargo container of unknown composition. If SNM is present in the container and the neutrons can reach it, high-energy fission neutrons will be detectable outside the cargo container. MCNP models indicate that even low-energy neutrons will be able to penetrate through reasonable amounts of material likely to be encountered in cargo environments. The only major exception is hydrogenous material, which could alter the radiation signature. The presence of shielding material may further alter these results. Small amounts of shielding that is hydrogenous will thermalize incident neutrons and raise the likelihood of generating fissions. An abundance of shielding material could mask the presence of fissile material but will also result in changes in the induced gamma energy spectrum and greatly increase the flux of thermal neutrons even outside the cargo container. Still, this material would not be resistant to other radiological techniques and the presence of an abundance of hydrogen will be evident and potentially raise suspicion in and of itself.
by Erik D. Johnson.
S.M.and S.B.
20
Nakatsuka, Noritsugu. « Isoscalar and Isovector strengths of low-energy dipole excitations in neutron-rich unstable 20O ». Kyoto University, 2018. http://hdl.handle.net/2433/232241.
Texte intégral
21
D'Angelo, Davide. « Towards the detection of low energy solar neutrinos in BOREXino data readout, data reconstruction and background identification / ». [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980146100.
Texte intégral
22
Wang, Chang-Kwang Chris. « A pilot study of an epithermal neutron source based on a low-energy proton accelerator for boron neutron capture therapy / ». The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487672631600438.
Texte intégral
23
Motta, Dario Giuseppe. « Feasibility analysis and prototype measurements of a novel approach for the real-time spectroscopy of low energy solar neutrinos ». [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971175403.
Texte intégral
24
Lavelle, Christopher M. « The neutronic design and performance of the Indiana University Cyclotron Facility (IUCF) Low Energy Neutron Source (LENS) ». [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3255512.
Texte intégralRésumé :
Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007.Title from PDF t.p. (viewed Nov. 20, 2008). Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1688. Adviser: David V. Baxter.
25
Remmes, Nicholas B. « Design of the Small Angle Neutron Scattering instrument at the Indiana University Low Energy Neutron Source : applications to the study of nanostructured materials / ». [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3297113.
Texte intégralRésumé :
Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007.Title from dissertation home page (viewed Sept. 30, 2008). Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1064. Adviser: David V. Baxter.
26
Anderson, Charlotte Rain. « The effects of introducing static and dynamic disorder on the low-energy excitations of superfluid â´He ». Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367070.
Texte intégral
27
Richard, Andrea L. « Measurement of the Breakup Cross Section of the D(d,n) Reaction at 6.94 MeV for the Active Interrogation of Hidden Fissile Materials ». Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1397479139.
Texte intégral
28
Joutras, David William. « An experimental search for low energy astrophysical neutrino sources ». 1987. http://catalog.hathitrust.org/api/volumes/oclc/15992900.html.
Texte intégralRésumé :
Thesis (Ph. D.)--University of Wisconsin--Madison, 1987.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 144-151).
29
Kos, Mark Szymon. « Low energy solar neutrino analysis of the salt phase of the Sudbury neutrino observatory ». Thesis, 2007. http://hdl.handle.net/1974/959.
Texte intégralRésumé :
The neutrino fluxes from the neutral current (NC), charged current (CC), and elastic scattering (ES) neutrino interactions in the salt phase of SNO have been extracted. The signals were extracted above an energy threshold of 4MeV, which is the lowest energy threshold at which the neutrino signals have been extracted from SNO to date. To achieve this low energy threshold the internal and external radioactive background signals have also been measured. The $^{8}$B neutrino fluxes for the 4MeV threshold were found to be
\begin{eqnarray*}
\Phi_{CC} & = & 1.60 ~^{+0.04}_{-0.04}~(\mbox{stat}) ~^{+0.06}_{-0.06}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1},\\
\Phi_{NC} & = & 4.84 ~^{+0.16}_{-0.16}~(\mbox{stat}) ~^{+0.29}_{-0.32}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1},\\
\Phi_{ES} & = & 2.75 ~^{+0.23}_{-0.23}~(\mbox{stat}) ~^{+0.25}_{-0.26}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1}.
\end{eqnarray*}
\noindent These results are in agreement with the values published in ~\cite{SNO3} and the NC flux is in agreement with the standard solar model calculation from ~\cite{bp2004}. The published fluxes were
\begin{eqnarray*}
\Phi_{CC} &= & 1.68 ~^{+0.06}_{-0.06}~(\mbox{stat}) ~^{+0.08}_{-0.09}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1} , \\
\Phi_{NC} &= & 4.94 ~^{+0.21}_{-0.21}~(\mbox{stat}) ~^{+0.38}_{-0.34}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1}, \\
\Phi_{ES} &= & 2.35 ~^{+0.22}_{-0.22}~(\mbox{stat}) ~^{+0.15}_{-0.15}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1}.
\end{eqnarray*}
\noindent The uncertainties on the extracted NC and CC fluxes are significantly smaller than on the published values. A comparison of the total uncertainty from flux measurements presented here and those published are given below.
\begin{table}[htp]
\begin{center}
\begin{tabular}{|c|c|c|} \hline
& uncertainties presented here (\%) & uncertainties from ~\cite{SNO3} (\%) \\ \hline
$\Phi_{CC}$ & $~^{+4.6}_{-4.4}$ & $~^{+5.9}_{-6.4}$ \\ \hline
$\Phi_{NC}$ & $~^{+6.8}_{-7.4}$ & $~^{+8.9}_{-8.2}$ \\ \hline
$\Phi_{ES}$ & $~^{+12.3}_{-12.6}$ & $~^{+11.3}_{-11.3}$ \\ \hline
\end{tabular}
\label{funcert1}
\end{center}
\end{table}
The shape of the CC energy spectrum has also been extracted with the 4MeV energy threshold. The uncertainties on the extracted fluxes are smaller than what was previously published. The CC spectrum gives a measure of the neutrino energy shape distortion due to neutrino oscillations. The uncertainties on the lowest energy bins in the extracted CC spectrum are much larger than the predicted distortion. We are therefore not sensitive to the upturn in the neutrino survival probability at lower energies predicted by neutrino oscillations in the large mixing angle (LMA) region.Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-12-19 13:58:16.601
30
Seibert, Stanley Reid. « A low energy measurement of the ⁸B solar neutrino spectrum at the Sudbury Neutrino Observatory ». 2008. http://hdl.handle.net/2152/17755.
Texte intégralRésumé :
The Sudbury Neutrino Observatory has previously shown that ⁸B solar neutrinos undergo flavor transformation between the Sun and the Earth. This work presents a joint analysis of one-third of the pure D₂O and salt phase data sets with an electron energy threshold of 3.5 MeV. A measurement of the neutral current interaction rate, sensitive to all neutrino flavors, gives a total ⁸B flux of 4.79 ± 0.22 (stat) ± 0.13(syst) × 10⁶ cm⁻²s⁻¹. This is in agreement with the prediction of the Standard Solar Model. For the first time we obtain the v[sunscript e] survival probability separately for downward-going (day) and upward-going (night) solar neutrinos. No significant distortion is observed day or night for ⁸B neutrinos with energies greater than 6 MeV. The lack of distortion, but overall suppression of electron neutrinos relative to the total flux, is consistent with matter-induced neutrino transformation in the Sun and the large mixing angle solution.text
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« Astrophysical neutrinos at the low and high energy frontiers ». Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.20985.
Texte intégralRésumé :
abstract: For this project, the diffuse supernova neutrino background (DSNB) has been calculated based on the recent direct supernova rate measurements and neutrino spectrum from SN1987A. The estimated diffuse electron antineutrino flux is ∼ 0.10 – 0.59 /cm2/s at 99% confidence level, which is 5 times lower than the Super-Kamiokande 2012 upper limit of 3.0 /cm2/s, above energy threshold of 17.3 MeV. With a Megaton scale water detector, 40 events could be detected above the threshold per year. In addition, the detectability of neutrino bursts from direct black hole forming collapses (failed supernovae) at Megaton detectors is calculated. These neutrino bursts are energetic and with short time duration, ∼ 1s. They could be identified by the time coincidence of N ≥2 or N ≥3 events within 1s time window from nearby (4 – 5 Mpc) failed supernovae. The detection rate of these neutrino bursts could get up to one per decade. This is a realistic way to detect a failed supernova and gives a promising method for studying the physics of direct black hole formation mechanism. Finally, the absorption of ultra high energy (UHE) neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel, is discussed. Results are applied to serval models of UHE neutrino sources. Suppression effects are strong for sources that extend beyond z ∼ 10. This provides a fascinating probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10 – 100. Ultimately this research will examine the detectability of DSNB, neutrino bursts from failed supernovae and absorption effects in the neutrino spectrum.Dissertation/Thesis
Ph.D. Physics 2013
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Maneschg, Werner [Verfasser]. « Low-energy solar neutrino spectroscopy with Borexino : towards the detection of the solar pep and CNO neutrino flux / put forward by Werner Maneschg ». 2011. http://d-nb.info/1012586359/34.
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Marta, Michele. « The 14N(p,γ)15O reaction studied at low and high beam energy ». Doctoral thesis, 2011. https://tud.qucosa.de/id/qucosa%3A25998.
Texte intégralRésumé :
The CNO cycle consists of a set of nuclear reactions that convert hydrogen into helium and releases energy in stars. The cycle contributes less than 1% to our Sun's luminosity, but it is responsible for detectable neutrino fluxes that can bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision.
The 14N(p,γ)15O is the slowest reaction in the CNO cycle and estabilishes its rate. The experimental study has been performed both at the LUNA 400 kV accelerator deep underground in the Gran Sasso mountain in Italy and at a 3 MV Tandetron in the Helmholtz-Zentrum Dresden-Rossendorf. A proton beam was sent on solid TiN targets and the prompt photons were collected by a composite HPGe detector (at LUNA) or by up to four HPGe detectors (Dresden).
The obtained results improve the fit of the excitation function in the R-matrix framework, that is used to extrapolate the S-factor at the very low astrophysical energies. In addition, the strength of two resonances at Ep = 430 and 897 keV of the 15N(p,αγ)12C reaction were measured, improving the precision for hydrogen depth profiling.
34
Kaleko, David. « MicroBooNE : The Search For The MiniBooNE Low Energy Excess ». Thesis, 2017. https://doi.org/10.7916/D87D3260.
Texte intégralRésumé :
This thesis describes work towards the search for a low energy excess of electromagnetic events in the MicroBooNE detector. A background primer on the current state of neutrino physics is provided, including a description of the MiniBooNE detector and its published observation of an excess of electromagnetic events at low energies. A description of the MicroBooNE Liquid Argon Time Projection Chamber (LArTPC) detector is given, along with a description of the event selection and reconstruction algorithms developed to select electron neutrino charge-current interactions. A MiniBooNE-like signal is simulated in MicroBooNE with assumptions about the origin of the excess, and the sensitivity to observe such a signal above backgrounds in MicroBooNE is computed. An additional analysis is presented which constrains a dominant background in the MicroBooNE low energy excess search: the beam-intrinsic electron neutrino interactions which come from kaon decay in the beam-line. An essential step in this analysis is to reconstruct the energy of muon neutrino charge-current interactions in which the muon produced in the interaction escapes the detector. A publication detailing the algorithm which leverages the phenomenon of multiple Coulomb scattering to reconstruct the energy of escaping muons is provided as an appendix.
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Seddighin, MARYAM. « Low Energy 8B Solar Neutrinos in SNO+ : Controlling and Constraining Radon Backgrounds ». Thesis, 2013. http://hdl.handle.net/1974/8016.
Texte intégralRésumé :
SNOLAB located in Sudbury, Canada, is hosting a new liquid scintillator experiment
for studying neutrinos which is called SNO+. Many interesting physics topics such as
measuring low energy solar neutrinos and searching for neutrinoless double beta decay
are expected to be performed using the SNO+ detector. SNO+ is designed to measure
the solar neutrino
flux at a lower energy range than SNO, and therefore it is able to
study LMA-MSW oscillations at this range of energy. This research is concerned with
extracting low energy 8B solar neutrinos while studying the tagging and reduction of
214Bi by 99.8%, one of the main backgrounds in the energy range of interest. Ways
to measure and control radon were also studied since it is the source of the 214Bi
background. Scintillation material, zinc sulfide, was selected for use in fabrication of
radon detectors known as Lucas cells. The fabrication of cover gas bags employed in
the SNO+ experiment to react to mine air pressure
fluctuations is described and the
interior radon emanation of these bags was measured and calculated.Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-05-01 20:26:56.981
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Harrison, David. « Low-Energy Proton Accelerator for Detector Testing ». 2013. http://hdl.handle.net/1993/22092.
Texte intégralRésumé :
Future fundamental physics experiments in neutron beta-decay require highly efficient detection of protons. Many of the experiments use electrostatic acceleration of the recoil protons into large-area silicon detectors for this purpose. A 30~keV proton accelerator was designed, created, and commissioned in order to characterize silicon detectors of this type. Final construction and initial results on the performance of the accelerator are presented. A unique aspect of the work is the use of a Penning ion generator as an ion source. The accelerator produced protons with momentum resolution ~1%. The ion source produced current stably, over a range of parameters, and over long periods of time. The accelerator achieved proton rates sufficient to calibrate silicon detectors.
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Hochmuth, Kathrin Angela [Verfasser]. « Low energy neutrinos as geological and astrophysical messengers / Kathrin Angela Hochmuth ». 2008. http://d-nb.info/989053342/34.
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CASENTINI, CLAUDIO. « Multimessenger search for astrophysical bursts with Gravitational Waves and Low Energy Neutrinos ». Doctoral thesis, 2018. http://hdl.handle.net/11573/1063714.
Texte intégralRésumé :
The next galactic Core Collapse Supernova (CCSN) may represent one of the
most important events in modern astrophysics. The electromagnetic (EM)
emission of the explosion is well understood, but we have no information
about the inner mechanisms that cause it. Neutrinos (\nu) and gravitational
waves (GWs) are the only messengers able to carry information about the inner
working mechanisms of a CCSN. Neutrinos from supernova carry thermodynamic
informations about the collapse, and GWs may reveal the dynamics
involved in the collapse. Via coincident detection and joint analysis
of \nu and GWs from the next nearby core collapse event, we will increase
the knowledge of the astrophysics, neutrino physics, and nuclear physics involved
in these sources.
In this thesis work, we studied the detection efficiency and the misidentification
of networks of \nu detectors to the same burst event, simulating the
detectors background and injecting signals produced using for the emission
a general description of an astrophysical burst of low-energy neutrinos with
a characteristic temporal structure and quasi-thermal spectral shape. We provide
a challenging method to better discriminate under threshold signals
from experimental background. With respect to previous search strategies
this method, without decreasing the detection efficiency, allows to knockingdown
the misidentification probability by a factor of 7, in the worse case,
within a distance of D \sim 20 kpc and, in the better case, this improvement
can reach a factor \sim 20 till an horizon of \si 75 kpc. After the definition of
the methodology to be used to construct the \nu network, we searched for coincident
events between GW data (archival data from LIGO and Virgo taken
before the upgrade to advanced detectors) and the correponding archival
data. We analyzed the obtained results, giving confidence intervals for the
observe coincident event.
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Hu, Xiaomin. « Multinuclei coherent effects on the widths and energy shifts on low energy neutron resonance ». Thesis, 1993. http://hdl.handle.net/1911/13741.
Texte intégralRésumé :
The exponentially decaying semi-stationary states of an assembly of identical classical radiators can have decay rates and resonant frequencies significantly different from that of an isolated radiator. These coherent effects on classical radiators emitting classical waves apply also to the particle processes in quantum limits, leading to the superradiant and subradiant modes with widths(decay rates) greatly enhanced or suppressed and resonant energies significantly shifted. The purpose of this thesis is to investigate these coherent effects on slow neutron-heavy nuclei interaction. A simple field model is introduced to show the coherent effects on the decay rates and resonant energies of two identical decaying states and on the neutron widths and resonant energies of neutron-two nuclei scattering. The latter case is also obtained by multiple scattering theory and is extended to a more general case of neutron-N nuclei scattering. The coherent effects on neutron width near Bragg angle in a crystal are also investigated.
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D'Angelo, Davide [Verfasser]. « Towards the detection of low energy solar neutrinos in BOREXino : data readout, data reconstruction and background identification / Davide D'Angelo ». 2006. http://d-nb.info/980146100/34.
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« The neutronic design and performance of the Indiana University Cyclotron Facility (IUCF) Low Energy Neutron Source (LENS) ». INDIANA UNIVERSITY, 2007. http://pqdtopen.proquest.com/#viewpdf?dispub=3255512.
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« Design of the Small Angle Neutron Scattering instrument at the Indiana University Low Energy Neutron Source : Applications to the study of nanostructured materials ». INDIANA UNIVERSITY, 2008. http://pqdtopen.proquest.com/#viewpdf?dispub=3297113.
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Niedermaier, Oliver Thomas [Verfasser]. « Low-energy Coulomb excitation of the neutron-rich Mg isotopes 30Mg and 32Mg / presented by Oliver Thomas Niedermaier ». 2005. http://d-nb.info/975806416/34.
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Stiegler, Tyana Michele. « Measurement of the Low Energy Nuclear Response in NaI(Tl) Crystals for Use in Dark Matter Direct Detection Experiments ». Thesis, 2013. http://hdl.handle.net/1969.1/151303.
Texte intégralRésumé :
The response of low energy nuclear recoil in NaI(Tl) is investigated in the following experiment. Such detectors have been used recently to search for evidence of dark matter in the form of weakly interacting massive particles (WIMPs). NaI(Tl) crystal response to nuclear recoil energy deposition is a key element in these searches. I discuss the cosmological and experimental motivations for these experiments, followed by an overview of the physics of direct detection and current relevant WIMP search experiments.
With the experiment motivations covered, the details of NaI(Tl) detectors are reviewed. The specifics of our experiment are laid out including the neutron production, neutron beam calibration, shielding optimization, experimental design and setup. Then the crystal response calibration studies and Geant4 simulations are discussed followed by the final quenching factor values and uncertainties.
This experiment measured quenching factors for sodium recoils in the energy range of (9 keV-40 keV) of 19%-27% QF. These results are similar to current published measurements. Interesting features of the QF measurements include an increase at low energies and a dip in the values at 30 keV, the iodine K-shell absorption edge. The goal of this experiment was to add valuable measurements of nuclear recoils at low energies that are relevant to low-mass WIMP experiments. Future plans will improve and expand on these measurements in order to better understand the response of NaI(Tl) at low energies.
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Motta, Dario Giuseppe [Verfasser]. « Feasibility analysis and prototype measurements of a novel approach for the real-time spectroscopy of low energy solar neutrinos / presented by Dario Giuseppe Motta ». 2004. http://d-nb.info/971175403/34.
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Laurin, Mathieu. « Recherche de la matière sombre à l’aide de détecteurs à liquides surchauffés dans le cadre de l’expérience PICO/Picasso ». Thèse, 2016. http://hdl.handle.net/1866/18480.
Texte intégralRésumé :
La matière sombre compte pour 85% de la matière composant l’univers et nous ne savons toujours pas ce qu’elle est. Depuis plusieurs années, l’expérience Picasso, maintenant devenue l’expérience PICO, tente d’élucider ce mystère. Les fréons de la famille des CXFY sont utilisés comme cibles de choix dans les détecteurs à liquides surchauffés de l’expérience PICO. Situés à SNOLab, en Ontario, ces détecteurs font parties des plus performant de la recherche de la matière sombre. Lors d’interactions de particules avec le liquide en surchauffe, un changement de phase est induit par le dépôt d’énergie engendré par l’interaction. Les bulles créées par l’évènement sont alors détectées par différents capteurs afin de déterminer le type d’interaction qui a eu lieu.
Dans ce travail seront présentés les détecteurs à liquides surchauffés dans le cadre de la recherche de la matière sombre. Principalement, nous y verrons trois types de détecteurs utilisés par les expériences PICO et Picasso. Le principe de
fonctionnement de chacun des détecteurs sera exposé en premier lieu ainsi que leur fabrication, puis leur mode d’opération et l’analyse des données. Les méthodes de calibration seront par la suite expliquées pour terminer avec une description des résultats obtenus démontrant la performance de ce type de détection.Dark matter makes up 85% of the matter content of the universe and we still don’t know what it is made of. The Picasso experiment, now named PICO, has been searching for it for several years with the use of superheated liquid detectors. Following the interaction of a particle with a superheated liquid freon of the CXFY family, a bubble is formed through a phase change and is detected with several types of sensors, telling us about the nature of the event. Located at SNOLab, in Ontario, these detectors produce some of the best results in the field. The present work will go through three types of superheated liquid detectors. A full description of the working principles will be presented for each of them. In addition, the fabrication, the operation mode and the data analysis will be shown. Detector calibration techniques will then be presented with different particle sources. Finally, the most recent results will be discussed, demonstrating the performance of the superheated liquid detector technique.
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Piro, Marie-Cécile. « Nouvelles limites sur la détection directe de la matière sombre avec l’expérience PICASSO ». Thèse, 2012. http://hdl.handle.net/1866/9138.
Texte intégralRésumé :
Les observations astronomiques et cosmologiques suggèrent fortement la présence d’une matière exotique, non-relativiste et non-baryonique qui représenterait 26% du contenu de masse-énergie de l’Univers actuel. Cette matière dite sombre et froide serait compo-
sée de particules neutres, massives et interagissant faiblement avec la matière ordinaire (WIMP : Weakly Interactive Massive Particles). Le projet PICASSO (Projet d’Identification des CAndidats Supersymétriques de la matière SOmbre) est une des expériences installées dans le site souterrain de SNOLAB à Sudbury en Ontario, qui tente de détecter directement un des candidats de la matière sombre, proposé dans le cadre des extensions supersymétriques du modèle standard : le neutralino. Pour cela, PICASSO utilise des détecteurs à gouttelettes surchauffées de C4F10, basés sur le principe de la chambre à bulles. Les transitions de phase dans les liquides surchauffés peuvent être déclenchées par le recul du 19 F, causé par une collision élastique avec les neutralinos. La nucléation
de la gouttelette génère une onde sonore enregistrée par des senseurs piézo-électriques. Cette thèse présentera les récents progrès de l’expérience PICASSO qui ont conduit à une augmentation substantielle de sa sensibilité dans la recherche du neutralino. En effet, de nouvelles procédures de fabrication et de purification ont permis de réduire à un facteur de 10, la contamination majeure des détecteurs, causée par les émetteurs alpha. L’étude de cette contamination dans les détecteurs a permis de localiser la source de ces émetteurs. Les efforts effectués dans le cadre de l’analyse des données, ont permis d’améliorer l’effet de discrimination entre des évènements engendrés par les particules alpha et par les reculs nucléaires. De nouveaux outils d’analyse ont également été implémentés dans le but de discriminer les évènements générés par des particules de ceux générés par des bruits de fond électroniques ou acoustiques. De plus, un mécanisme important de suppression de bruit de fond indésirable à haute température, a permis à l’expérience PICASSO d’être maintenant sensible aux WIMPs de faibles masses.Astronomical and cosmological observations strongly suggest the presence of an exotic form of non-relativistic, non-baryonic matter that would represent 26% of the actual energy-matter content of the Universe. This so-called cold dark matter would be composed of Weakly Interactive Massive Particles (WIMP). PICASSO (Project In CAnada to Search for Supersymmetric Objects) aims to detect directly one of the dark matter candidates proposed in the framework of supersymmetric extensions of the standard model : the neutralino. The experiment is installed in the SNOLAB underground laboratory at Sudbury (Ontario) and uses superheated C4F10 droplets detectors, a variant of bubble chamber technique. Phase transitions in the superheated liquids are triggered by 19 F recoils caused by the elastic collision with neutralinos and create an acoustic signal which is recorded by piezoelectric sensors. This thesis presents recent progress in PICASSO leading to a substantially increased sensitivity in the search of neutralinos. New fabrication and purification procedures allowed a background reduction of about a factor 10 of the major detectors contamination caused by alpha emitters. Detailed studies allowed to localize these emitters in the detectors. In addition, data analysis efforts were able to improve substantially the discrimination between alpha particle induced events and those created by nuclear recoils. New analysis tools were also developed in order to discriminate between particle induced and non-particle induced events, such as electronic backgrounds and acoustic noise signals. An important new background suppression mechanism at higher temperatures led to the present improved sensitivity of PICASSO at low WIMP masses.
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Lee, Nan Young. « Polarized Compton Scattering off the Nucleon ». Doctoral thesis, 2001. http://hdl.handle.net/11858/00-1735-0000-0006-B42F-F.
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