Entropy for SU(3)cSU(3)_c Quark States

We discuss the quantum state structure using the standard model for three colored quarks in the fundamental representations of $SU(3)_c$ making up the singlet ground state of the hadrons. This allows us to calculate a finite von Neumann entropy from the quantum reduced density matrix, which we explicitly evaluate for the quarks in a model for the meson and baryon states. Finally we look into the general effects and implications of entanglement in the $SU(3)_c$ color space.Comment: 9 pages, 0 figure

Light bottom squark and gluino confront electroweak precision measurements

We address the compatibility of a light sbottom (mass 2\sim 5.5 \gev) and a light gluino (mass 12\sim 16 \gev) with electroweak precision measurements. Such light particles have been suggested to explain the observed excess in the $b$ quark production cross section at the Tevatron. The electroweak observables may be affected by the sbottom and gluino through the SUSY-QCD corrections to the $Zbb$ vertex. We examine, in addition to the SUSY-QCD corrections, the electroweak corrections to the gauge boson propagators from the stop which are allowed to be light from the SU(2)$_L$ symmetry. We find that this scenario is strongly disfavored from electroweak precision measurements unless the heavier sbottom mass eigenstate is lighter than 180\gev and the left-right mixing in the stop sector is sufficiently large. This implies that one of the stops should be lighter than about 98\gev.Comment: 4 pages, revtex, 2 figures. Reference added, version to appear in Phys.Rev.Let

Experimental limits on New Physics from charm decay

Recent measurements in the charm sector are reviewed, concentrating on results which are sensitive to New Physics effects. The scope of the presentation includes D0-D0bar mixing searches, a CPT / Lorentz invariance study, and a range of searches for rare and forbidden decays. Results from the BaBar, Belle, CDF, CLEO, and FOCUS collaborations are presented, including an important first observation.Comment: 14 pages, 5 tables, 17 figures. Invited talk presented at the 21st International Symposium On Lepton And Photon Interactions At High Energies (LP03) 11-16 August 2003, Batavia, Illinois. To appear in the proceedings of the symposiu

Calculation of HELAS amplitudes for QCD processes using graphics processing unit (GPU)

We use a graphics processing unit (GPU) for fast calculations of helicity amplitudes of quark and gluon scattering processes in massless QCD. New HEGET ({\bf H}ELAS {\bf E}valuation with {\bf G}PU {\bf E}nhanced {\bf T}echnology) codes for gluon self-interactions are introduced, and a C++ program to convert the MadGraph generated FORTRAN codes into HEGET codes in CUDA (a C-platform for general purpose computing on GPU) is created. Because of the proliferation of the number of Feynman diagrams and the number of independent color amplitudes, the maximum number of final state jets we can evaluate on a GPU is limited to 4 for pure gluon processes ($gg\to 4g$), or 5 for processes with one or more quark lines such as $q\bar{q}\to 5g$ and $qq\to qq+3g$. Compared with the usual CPU-based programs, we obtain 60-100 times better performance on the GPU, except for 5-jet production processes and the $gg\to 4g$ processes for which the GPU gain over the CPU is about 20

Search for rare leptonic B decays at the Tevatron

Results of a search for the Flavor-Changing Neutral Current decay $B^0_{s,d} \to \mu^+ \mu^-$ using $p\bar{p}$ collision data at $\sqrt{s}=1.96$ TeV collected at Fermilab Tevatron collider by the CDF and D{\O}detectors are presented. CDF reports upper limits on ${\cal B} (B^0_{s} \to \mu^+ \mu^-) \leq 7.5 \cdot10^{-7}$ and ${\cal B}(B^0_{d} \to \mu^+ \mu^-) \leq 1.9 \cdot10^{-7}$ at the 95% C.L. using 171 pb$^{-1}$. The D{\O}Collaboration used 240 pb$^{-1}$ to set an even more stringent limit on the branching ratio for $B^0_{s} \to \mu^+ \mu^-$ of $5.0\cdot 10^{-7}$ at the 95% C.L.Comment: 5 pages, 2 figures, submitted to DPF 2004 conference proceedings, UC Riverside, C

Energy diffusion in frustrated quantum spin chains exhibiting Gaussian orthogonal ensemble level statistics

Frustrated quantum $XXZ$ spin chains with the next-nearest-neighbor (NNN) couplings are typically deterministic many-body systems exhibiting Gaussian orthogonal ensemble (GOE) spectral statistics. We investigate energy diffusion for these spin chains in the presence of a periodically oscillating magnetic field. Diffusion coefficients are found to obey the power law with respect to both the field strength and driving frequency with its power varying depending on the linear response and non-perturbative regimes. The widths of the linear response and the non-perturbative regimes depend on the strength of frustrations. We have also elucidated a mechanism for oscillation of energy diffusion in the case of weakened frustrations.Comment: 6 pages, 6 figure

Consequences of a Possible Di-Gamma Resonace at TRISTAN

If high mass di-gamma events observed at LEP are due to the production of a di-gamma resonance via its leptonic coupling, its consequences can be observed at TRISTAN. We find that a predicted $Z$ decay branching rate is too small to account for the observed events if the resonance spin is zero, due to a strong cancellation in the decay amplitudes. Such a cancellation is absent if the resonance has a spin two. We study the consequences of a tensor production in the processes $e^+e^- \to e^+e^-$, $\mu^+\mu^-$ and $\gamma\,\gamma$ at TRISTAN energies. Complete helicity amplitudes with tensor boson exchange contributions are given, and the signal can clearly be identified from various distributions. TRISTAN experiments are also sensitive to the virtual tensor boson exchange effects, which reduce to the contact interaction terms in the high mass limit.Comment: 23 pages in revtex, 7 figures (not included) available upon request, KEK-TH-35

Weak boson fusion production of supersymmetric particles at the LHC

We present a complete calculation of weak boson fusion production of colorless supersymmetric particles at the LHC, using the new matrix element generator SUSY-MadGraph. The cross sections are small, generally at the attobarn level, with a few notable exceptions which might provide additional supersymmetric parameter measurements. We discuss in detail how to consistently define supersymmetric weak couplings to preserve unitarity of weak gauge boson scattering amplitudes to fermions, and derive sum rules for weak supersymmetric couplings.Comment: 24 p., 3 fig., 9 tab., published in PRD; numbers in Table IV corrected to those with kinematic cuts cite