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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Search for Baryon Number Violation in Tellurium-130 with CUORE

Sharma, Vivek 13 May 2024 (has links)
CUORE is one of the world-leading experiments to search for neutrinoless double beta decay. The excellent energy resolution and the stability of the detectors at CUORE also allow for other rare event searches. This thesis describes an experimental analysis undertaken to search for baryon number violation in 130Te using the data acquired by the CUORE detector. The conservation of the baryon number in the Standard Model relies on an accidental symmetry rather than being deduced from fundamental principles. If there is evidence suggesting a breach of this symmetry, it would significantly impact our understanding of the universe, especially concerning the origin of the matter-antimatter asymmetry. One possible way for this conservation principle to be violated is through tri-nucleon decay, where three nucleons decay simultaneously within a nucleus. For 130Te, the resulting decay products would be emitted with energy in the GeV range, making them a promising signal for detection in the CUORE experiment. This thesis describes the search signatures, the relevant background, and the analysis techniques used in this investigation, and results for an exposure of 236.6 kg·yr are presented. The daughter nucleus of the decay (127In) is unstable, and its decay chain can offer an secondary signature coinciding with the emitted energy. The viability of adding this secondary signature is also presented. / Doctor of Philosophy / Since the beginning of scientific thought, humankind has asked why there is something in the Universe instead of nothing. As our understanding of the working principles of the Universe deepened, this question has been refined and focused on an intriguing imbalance easily ob- served around us: The imbalance of the quantity of matter over anti-matter. We have never observed anti-matter galaxies or stars, and we never observe anti-matter manifesting around us in our daily lives. There are many ideas physicists have developed to explain this mysteri- ous absence of anti-matter, and one of them involves searching for an extremely rare radioac- tive process called triple nucleon decay. This thesis uses the data acquired by the nuclear experiment CUORE, situated in the Gran Sasso mountains in Italy, to look for this process.
22

Robust Measurement of the Cosmic Distance Scale Using Baryon Acoustic Oscillations

Xu, Xiaoying January 2012 (has links)
We present techniques for obtaining precision distance measurements using the baryon acoustic oscillations (BAO) through controlling systematics and reducing statistical uncertainties. Using the resulting distance-redshift relation, we can infer cosmological parameters such as w, the equation of state of dark energy. We introduce a new statistic, ɷ(l)(r(s)), for BAO analysis that affords better control over systematics. It is computed by band-filtering the power spectrum P(k) or the correlation function ξ(r) to extract the BAO signal. This is conducive to several favourable outcomes. We compute ɷ(l)(r(s)) from 44 simulations and compare the results to P(k) and ξ(r). We find that the acoustic scales and theoretical errors we measure are consistent between all three statistics. We demonstrate the first application of reconstruction to a galaxy redshift survey. Reconstruction is designed to partially undo the effects of non-linear structure growth on the BAO, allowing more precise measurements of the acoustic scale. We also present a new method for deriving a smooth covariance matrix based on a Gaussian model. In addition, we develop and perform detailed robustness tests on the ξ(r) model we employ to extract the BAO scale from the data. Using these methods, we obtain spherically-averaged distances to z = 0.35 and z = 0.57 from SDSS DR7 and DR9 with 1.9% and 1.7% precision respectively. Combined with WMAP7 CMB observations, SNLS3 data and BAO measurements from 6dF, we measure w = -1.08 ± 0.08 assuming a wCDM cosmology. This represents a ~8% measurement of w and is consistent with a cosmological constant.The preceding does not capture the expansion history of the universe, H(z), encoded in the line-of-sight distance scale. To disentangle H(z), we exploit the anisotropic BAO signal that arises if we assume the wrong cosmology when calculating the clustering distribution. Since we expect the BAO signal to be isotropic, we can use the magnitude of the anisotropy to separately measure H(z) and D(A)(z). We apply our simple models to SDSS DR7 data and obtain a ~3.6% measurement of D(A)(z=0.35) and a ~8.4% measurement of H(z = 0.35).
23

Baryon stopping and quark gluon plasma production at RHIC and LHC

Ljachov, Konstantin. Unknown Date (has links) (PDF)
Frankfurt (Main), University, Diss., 2008.
24

Dark and Luminous Matter in Galaxies and Large Scale Structure

Jiang, Guangfei 08 September 2008 (has links)
No description available.
25

The baryonic matter and geometry of the local group

Tronrud, Thorold 13 March 2019 (has links)
First, the baryonic content of simulated halos of virial masses between 5 x 10^{9} M_{\odot}$ to 5 x 10^{12} M_{\odot}$ in the APOSTLE project is examined in the context of the missing baryon problem. Baryonic particles in APOSTLE can be either stars or gas. Non-star-forming gas, or the circumgalactic medium (CGM) is further classified by temperature into the Cool CGM (CCGM, T < 10^{5} K), or the Warm-Hot CGM (WHCGM, T > 10^{5} K). APOSTLE halos are found to contain less than 60% of the expected mass of baryons (f_{b} = Ω{b}/Ω{m}, M_{b} = f_{b} x M_{200}) within their virial radius. The WHCGM contains 29% ± 10%, the CCGM 12% ± 5%, and the stars and star-forming gas 19% ± 5%. The metal content of the same halos is analyzed, and compared to the total metals produced by the stars within the virial radius. Over two thirds of the produced metals are retained within the halo, with 14% ± 3% in the WHCGM, 13% ± 4% in the CCGM, and 43% ± 9% in the stars and star-forming gas. Next, we focus on the overall distribution of matter within a 3Mpc radius from the Milky Way. Using the trends in APOSTLE volumes, I quantify both the ellipticity and orientation of this spatial distribution using the principal axes of the inertia tensor of the positions of these galaxies. The Zone of Avoidance has little impact on this result, and the short axis is aligned with that of the Supergalactic Plane, and is perpendicular to the vector separating the Milky Way and Andromeda galaxies. APOSTLE local group analogues are found to be similarly anisotropic, and like in the observed Local Group, the minor axis of that distribution is found to be perpendicular to the vector separating the two primaries. The angular momentum of the stellar disk shows weak alignment with the minor axis of the field galaxy distribution. In addition the simulations also suggest that the angular momenta of the two primary dark-matter halos tend to be anti-aligned. Additionally, stellar disks tend to orient themselves in the same direction as their halo. / Graduate
26

Study of strange particule production in jets with the alice experiment at the LHC / Étude de la production des particules étranges dans des jets avec l'expérience ALICE auprès du LHC

Kucera, Vit 15 November 2016 (has links)
Le plasma de quarks et de gluons est un état de matière obtenu lors de températures et de densités d’énergie extrêmes où les quarks et les gluons sont libres. Cette matière chaude et dense peut être créée dans les collisions d’ions lourds ultra-relativistes. Les mesures des spectres des particules identifiées produites dans des jets représentent un outil majeur permettant d'étudier les propriétés du plasma créé dans les collisions et d'ainsi comprendre les relations entre divers mécanismes contribuant à la production de particules dans ce milieu. Cette thèse présente une analyse des spectres en impulsion transverse des baryons Λ et mésons K0S produits dans des jets chargés lors de collisions Pb–Pb centrales à l'énergie sqrt(sNN) = 2.76 TeV mesurées avec ALICE au LHC. Les résultats sont utilisés pour discuter l'origine de l'augmentation du rapport entre baryons et mésons observée pour la production inclusive des particules dans les collisions d’ions lourds ultra-relativistes. / Quark–gluon plasma is a state of matter existing under extreme energy densities and temperatures where quarks and gluons are deconfined. This hot and dense strongly interacting matter can be created in ultra-relativistic heavy-ion collisions. Measurements of spectra of identified particles produced in jets represent a major tool for studying properties of the plasma created in the collisions and for understanding the interplay of various mechanisms which contribute to the particle production in this medium. In this thesis, we present the measurement of the transverse-momentum spectra of Λ baryons and K0S mesons produced in charged jets in central Pb–Pb collisions at the centre-of-mass energy sqrt(sNN) = 2.76 TeV, measured with ALICE at the LHC. The results of the analysis are used to discuss the origin of the enhancement of the baryon-to-meson ratio observed for the inclusive production of light-flavour particles in ultra-relativistic heavy-ion collisions.
27

Charmed baryon resonances and mesons in hot and dense matter

Jiménez Tejero, Clara Estela 05 March 2012 (has links)
In this thesis we have studied baryon resonances generated from the dynamical interaction of two hadrons. We are interested on this study as an alternative approach to explain the increasing number of observed charmed states which apparently do not fit into the traditional three quark picture of a baryon. In particular, we study baryon molecules with JP = ½ - which can be formed from the attractive interaction of a pseudoscalar meson (0-) and a ground state baryon (1/2+) in s-wave (L = 0). Therefore our aim is to contribute to the understanding of the observed charm baryon spectra by checking if the dynamical origin can explain those states which are candidates to be a baryon resonance with JP =1/2-. The important feature of our model is the description of the meson-baryon interaction in terms of the t-channel vector meson exchange which is fully solved without any approximation. The first part of the thesis is devoted to study these sort of baryon molecules in free space. In order to learn about the nature of a baryon it is important to study its different types of decays. For this reason, we will calculate the strong decays of dynamically generated resonances into meson-baryon components, as well as the electromagnetic transition of such hadron molecules into the lowest-lying ground states. In the second part of the thesis we have included medium and temperature effects on the formalism to study the properties of the charmed baryon resonant states in hot and dense matter. This will allow us as well to study the properties of charmed mesons (D, D, Ds and Ds) in the nuclear medium which will be simultaneously dressed in the self-consistent calculation for the first time. The behaviour of these mesons will influence the charmonium production whose suppression is connected with the possible formation of quark-gluon plasma at a dense matter and high temperature scenario. / En esta tesis se han estudiado las resonancias bariónicas generadas a partir de la interacción dinámica de dos hadrones. Estamos interesados en este estudio como un enfoque alternativo para explicar el creciente número de estados observados con quark encanto y que aparentemente no encajan en la imagen tradicional de tres quarks de un barión. En particular, se estudian las moléculas de bariones con JP = ½ - que pueden formarse a partir de la interacción atractiva de un mesón pseudoescalar (0-) y un barión del estado fundamental ( 1/2+) en onda s (L = 0). Por tanto, nuestro objetivo es comprobar si el origen dinámico puede explicar aquellos estados que son candidatos a ser una resonancia bariónica con JP =1/2-. La característica importante del modelo es la descripción de la interacción mesón-barión en términos del canal t de intercambio de mesones vectoriales, que está resuelto sin ningún tipo de aproximación.La primera parte de la tesis está dedicada a estudiar este tipo de moléculas en el espacio libre. Con el fin de aprender sobre la naturaleza de un barión es importante estudiar sus diferentes tipos de desintegración. Por esta razón, calculamos las desintegraciones fuertes de las resonancias en canales mesón-barión, así como la transición electromagnética a bariones de estado fundamental.En la segunda parte de la tesis se ha incluido en el formalismo los efectos del medio y de la temperatura para estudiar las propiedades de los estados de bariones encantados en materia caliente y densa. Esto nos permitirá también estudiar las propiedades de los mesones encantados (D, D, Ds y Ds) en el medio nuclear, que serán vestidos autoconsistentemente en el cálculo por primera vez. El comportamiento de estos mesones influirá en la producción de “charmonium”, cuya supresión está relacionada con la posible formación de plasma de quark-gluón en materia densa y caliente.
28

Measuring angular diameter distances in the universe by Baryon Acoustic Oscillation and strong gravitational lensing

Jee, Inh 2013 August 1900 (has links)
We discuss two ways of measuring angular diameter distances in the Universe: (i) Baryon Acoustic Oscillation (BAO) , and (ii) strong gravitational lensing. For (i), we study the effects of survey geometry and selection functions on the 2-point correlation function of Lyman- alpha emitters in 1.9 < z < 3.5 for Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We develop a method to extract the BAO scale (hence a volume-averaged angular diameter distance D_V, which is a combination of the angular diameter distance and the Hubble expansion rate, i.e., [cz〖(1+z)〗^2 〖D_A〗^2 H^(-1) ]^(1/3)) from a spherically averaged 1-d correlation function. We quantify the statistical errors on such measurements. By using log-normal realizations of the HETDEX dataset, we show that we can determine DV from HETDEX at 2% accuracy using the 2-point correlation function. This study is complementary to the on-going effort to characterize the power spectrum using HETDEX. For (ii), a previous study (Para ficz and Hjorth 2009) looked at the case of a spherical lens following a singular isothermal distribution of matter and an isotropic velocity distribution, and found that combining measurements of the Einstein ring radius with the time delay of a strong lens system directly leads to a measurement of the angular diameter distance, D_A. Since this is a very new method, it requires more careful investigations of various real-world eff ects such as a realistic matter density pro file, an anisotropic velocity distribution, and external convergence. In more realistic lens confi gurations we find that the velocity dispersion is the dominant source of the uncertainty ; in order for this method to achieve competitive precision on measurements of DA, we need to constrain the velocity dispersion, down to the percent level. On the other hand, external convergence and velocity dispersion anisotropy have negligible e ect on our result. However, we also claim that the dominant source of the uncertainty depends largely on the image con figuration of the system, which leads us to the conclusion that studying the angular dependence of the lens mass distribution is a necessary component. / text
29

High-Precision Large-Scale Structure: The Baryon Acoustic Oscillations and Passive Flow

Seo, Hee-Jong January 2007 (has links)
We present a precision study of large-scale structure from large galaxy redshift surveys. We focus on two main subjects of large-scale structure: precisioncosmology with baryon acoustic oscillations from large galaxy surveys and the evolution of galaxy clustering for passively flowing galaxies.The baryon acoustic oscillations in galaxy redshift surveys can serve as an efficient standard ruler to measure the cosmological distance scale, i.e., theangular diameter distances and Hubble parameters, as a function of redshift, and therefore dark energy parameters. We use a Fisher matrix formalism to show that such a standard ruler tests can constrain the angular diameter distances and Hubble parameters to a precision of a few percent, thereby providing robust measurements of present-day dark energy density and its time-dependence.We use N-body simulations to investigate possible systematic errors in the recovery of the cosmological distance scale from galaxy redshift surveys. We show that the baryon signature on linear and quasi-linear scales is robust against nonlinear growth, redshift distortions, and halo (or galaxy) bias, albeit partial obscuration of the signature occurs due to nonlinear growth and redshift distortions.We present the improved Fisher matrix formalism which incorporates the Lagrangian displacement field to describe the nonlinear effects on baryon signature as a function of time and scale. We present a physically motivated, reduced 2-dimensional fitting formula for the full Fisher matrix formalism. We show that distance precision from the revised formalism is in excellent agreement with distance precision from N-body simulations.Finally, we present a numerical study of the evolution of galaxy clustering when galaxies flow passively from high redshift to low redshift, that is, without merging or new formations. We show that passive flow evolution induces interesting characteristics in the galaxy distribution at low redshift: we find an asymptotic convergence in galaxy clustering and halo occupation distribution regardless of the initial distribution of galaxies.
30

Measurement of charmed hadron production in e±p deep inelastic scattering with the ZEUS detector

Allfrey, Philip Daniel January 2007 (has links)
Charmed hadron production has been studied in 225 pb<sup>-1</sup> of data collected with the ZEUS detector in the HERA-II runnning period. Studies were made in the D* → D<sup>0</sup>π → Kππ decay channel to determine the potential for the microvertex detector to improve charm signals. Integrated cross sections were measured for the decays D<sup>0</sup> → K<sup>0</sup><sub>s</sub>π⁺ π⁻, D<sup>±</sup> → K<sup>0</sup><sub>s</sub> π<sup>±</sup>, D<sup>±</sup>_s → K<sup>0</sup>s K<sup>±</sup> and Lambda<sup>±</sup>_c → Lambda<sup>0</sup>π<sup>±</sup> in the kinematic region 5< Q² < 1000 GeV², 0.02 < y < 0.7, 1.5 < pT(D,Lambda_c) < 20.0 GeV, -1.6 < pseudorapidity(D, Lambda_c) < 1.6. The D<sup>0</sup> cross section was additionally measured down to pT(D<sup>0</sup>) > 1.0 GeV. Differential cross sections as a function of Q², x, pT(D) and pseudorapidity(D) were measured for the D<sup>0</sup>, D<sup>±</sup>, and D_s<sup>±</sup> channels. The measurements were compared to next-to-leading order (NLO) QCD calculations, and good agreement found for all variables in all channels over the measured kinematic region. The strangeness-suppression factor, gamma_s = D_s<sup>±</sup>/(D<sup>±</sup> + D<sup>0</sup>), was measured and found to be in good agreement with values previously measured at HERA and elsewhere, and with the DJANGOH and RAPGAP Monte Carlo. The ratio of charmed baryons to mesons, Lambda_c<sup>±</sup>/(D<sup>±</sup> + D<sup>0</sup>), was measured and also found to be in good agreement with Monte Carlo.

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