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S. D. Katz

Publications and source records attributed to S. D. Katz.

103 records · Page 6Linked to original sources
arXiv2002

Determination of absolute neutrino masses from Z-bursts

Ultrahigh energy neutrinos (UHEν) scatter on relic neutrinos (Rν) producing Z bosons, which can decay hadronically producing protons (Z-burst). We compare the predicted proton spectrum with the observed ultrahigh energy cosmic ray (UHECR) spectrum and determine the mass of the heaviest Rνvia a maximum likelihood analysis. Our prediction depends on the origin of the power-like part of the UHECR spectrum: m_ν=2.75^{+1.28}_{-0.97} eV for Galactic halo and 0.26^{+0.20}_{-0.14} eV for extragalactic (EG) origin. The necessary UHEνflux should be detected in the near future.

hep-ph↗
arXiv2002

Finite temperature and chemical potential in lattice QCD and its critical point

We propose a method to study lattice QCD at finite temperature (T) and chemical potential (μ). We compare the method with direct results and with the Glasgow method by using n_f=4 QCD at Im(μ)\neq0. We locate the critical endpoint (E) of QCD on the Re(μ)-T plane. We use n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices. Our results are based on {\cal{O}}(10^3-10^4) configurations.

nucl-th↗
arXiv2001

The critical point of lattice QCD on the μ-T plane

We propose a method to study lattice QCD at finite temperature and chemical potential. We compare it with direct results and with the Glasgow method by using n_f=4 QCD at Im(μ)\neq 0. We locate the critical endpoint (E) of QCD on the Re(μ)-T plane. In this study we use n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices.

hep-lat↗
arXiv2001

Lattice QCD at finite T and μand the critical point of QCD

We propose a method to study lattice QCD at finite T and μ. We compare it with direct results and with the Glasgow method by using n_f=4 QCD at Im(μ)\neq 0. We locate the critical endpoint (E) of QCD on the Re(μ)-T plane. In this study we use n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices.

hep-lat↗
arXiv2001

Four-dimensional lattice results on the MSSM electroweak phase transition

We present the results of our large scale 4-dimensional (4d) lattice simulations for the MSSM electroweak phase transition (EWPT). We carried out infinite volume and continuum limit extrapolations and found a transition whose strength agrees well with perturbation theory. We determined the properties of the bubble wall that are important for a successful baryogenesis.

hep-ph↗
arXiv2001

Possible detection of relic neutrinos and determination of their mass: quantitative analysis

We consider the possibility that a large fraction of the ultrahigh energy cosmic rays are decay products of Z bosons which were produced in the scattering of ultrahigh energy cosmic neutrinos on cosmological relic neutrinos. We compare the observed ultrahigh energy cosmic ray spectrum with the one predicted in the above Z-burst scenario and determine the mass of the heaviest relic neutrino as well as the necessary ultrahigh energy cosmic neutrino flux via a maximum likelihood analysis.

hep-ph↗
arXiv2001

Propagation of ultrahigh energy cosmic rays and compact sources

The clustering of ultrahigh energy (>10^{20} eV) cosmic rays (UHECR) suggests that they might be emitted by compact sources. Statistical analysis (Dubovsky et al., 2000) estimated the source density. We extend their analysis to give also the confidence intervals (CI) for the source density using a.) no assumptions on the relationship between clustered and unclustered events; b.) nontrivial distributions for the source luminosities and energies; c.) the energy dependence of the propagation. We also determine the probability that a proton created at a distance r with energy E arrives at earth above a threshold E_c. Using this function one can determine the observed spectrum just by one numerical integration for any injection spectrum. The observed 14 UHECR events above 10^{20} eV with one doublet gives for the source densities 180_{-165}^{+2730}\cdot 10^{-3} Mpc^{-3} (on the 68% confidence level).

hep-ph↗
arXiv2001

Ultrahigh energy cosmic rays as a Grand Unification signal

We analyze the spectrum of the ultrahigh energy (above \approx 10^{9} GeV) cosmic rays. With a maximum likelihood analysis we show that the observed spectrum is consistent with the decay of extragalactic GUT scale particles. The predicted mass for these superheavy particles is m_X=10^b GeV, where b=14.6_{-1.7}^{+1.6}.

hep-ph↗
arXiv2001

Astroparticle physics signals beyond the Standard Model

In this thesis two signals pointing beyond the Standard Model are discussed. The first signal is the presence of baryonic matter around us. The possibility of baryogenesis in the Minimal Supersymmetric Standard Model (MSSM) was studied. The bosonic part of the MSSM Lagrangian was put on the lattice. Finite temperature and zero temperature simulations were performed to find the jump of the Higgs length and the mass spectrum. The phase diagram of MSSM in the m_U^2 - T plane was determined. The properties of the bubble wall during the phase transition were also analyzed. The second signal that is discussed in this thesis comes from the observed cosmic rays. According to the so-called ''top-down'' scenarios, the highest energy cosmic rays can be the decay products of some metastable superheavy particle. Based on the clustering features of the detected events, first the source density was determined. Then the mass of the decaying superheavy particle was found which is in rough agreement with the grand unification scale. The lattice simulations of MSSM require a large amount of CPU time. A PC based supercomputer was built at the Eötvös University to solve this problem. The hardware and software architecture as well as the performance of the machine is discussed.

hep-ph↗
arXiv2000

Ultra High Energy Cosmic Rays from Compact Sources

The clustering of ultra high energy (above 10^20 eV) cosmic rays (UHECR) suggests that they might be emitted by compact sources. Statistical analysis of Dubovsky et al. (Phys. Rev. Lett. 85 (2000) 1154) estimated the source density. We extend their analysis to give also the confidence intervals for the number of sources using a.) no assumptions on the relationship between clustered and unclustered events; b.) nontrivial distributions for the source intensities and energies; c.) the energy dependence of the propagation. We determine the probability that a proton created at a distance r with energy E arrives at earth above a threshold E_c. Using this function one can determine the observed spectrum just by one numerical integration for any injection spectrum. The observed 14 UHECR events above 10^20 eV with one doublet gives for the source densities 180_-165^+2730*10^-3 Mpc^-3 (on the 68% confidence level). We present detailed results for future experiments with larger UHECRs statistics.

hep-ph↗
arXiv2000

Electroweak Phase Transition in the MSSM: 4-Dimensional Lattice Simulations

Recent lattice results have shown that there is no Standard Model (SM) electroweak phase transition (EWPT) for Higgs boson masses above \approx 72 GeV, which is below the present experimental limit. According to perturbation theory and 3-dimensional (3d) lattice simulations there could be an EWPT in the Minimal Supersymmetric Standard Model (MSSM) that is strong enough for baryogenesis up to m_h \approx 105 GeV. In this letter we present the results of our large scale 4-dimensional (4d) lattice simulations for the MSSM EWPT. We carried out infinite volume and continuum limits and found a transition whose strength agrees well with perturbation theory, allowing MSSM electroweak baryogenesis at least up to m_h = 103 \pm 4 GeV. We determined the properties of the bubble wall that are important for a successful baryogenesis.

hep-ph↗
arXiv2000

The PMS project: Poor Man's Supercomputer

We briefly describe the Poor Man's Supercomputer (PMS) project carried out at Eotvos University, Budapest. The goal was to develop a cost effective, scalable, fast parallel computer to perform numerical calculations of physical problems that can be implemented on a lattice with nearest neighbour interactions. To this end we developed the PMS architecture using PC components and designed a special, low cost communication hardware and the driver software for Linux OS. Our first implementation of PMS includes 32 nodes (PMS1). The performance of PMS1 was tested by Lattice Gauge Theory simulations. Using SU(3) pure gauge theory or bosonic MSSM on PMS1 we obtained 3$/Mflop and 0.45$Mflop price-to-sustained performance for double and single precision operations, respectively. The design of the special hardware and the communication driver are freely available upon request for non-profit organizations.

hep-lat↗