Dark Matter Time Projection Chamber : Recent R&D Results

The Dark Matter Time Projection Chamber collaboration recently reported a dark matter limit obtained with a 10 liter time projection chamber filled with CF[subscript 4] gas. The 10 liter detector was capable of 2D tracking (perpendicular to the drift direction) and 2D fiducialization, and only used information from two CCD cameras when identifying tracks and rejecting backgrounds. Since that time, the collaboration has explored the potential benefits of photomultiplier tube and electronic charge readout to achieve 3D tracking, and particle identification for background rejection. The latest results of this effort is described here

The QCD transition temperature: results with physical masses in the continuum limit II.

We extend our previous study [Phys. Lett. B643 (2006) 46] of the cross-over temperatures (T_c) of QCD. We improve our zero temperature analysis by using physical quark masses and finer lattices. In addition to the kaon decay constant used for scale setting we determine four quantities (masses of the \Omega baryon, K^*(892) and \phi(1020) mesons and the pion decay constant) which are found to agree with experiment. This implies that --independently of which of these quantities is used to set the overall scale-- the same results are obtained within a few percent. At finite temperature we use finer lattices down to a <= 0.1 fm (N_t=12 and N_t=16 at one point). Our new results confirm completely our previous findings. We compare the results with those of the 'hotQCD' collaboration.Comment: 19 pages, 8 figures, 3 table

Measurement of the polar-angle distribution of leptons from W boson decay as a function of the W transverse momentum in proton-antiproton collisions at sqrt{s}=1.8 TeV

We present a measurement of the coefficient alpha_2 of the leptonic polar-angle distribution from W boson decays, as a function of the W transverse momentum. The measurement uses an 80+/-4 pb^{-1} sample of proton-antiproton collisions at sqrt{s}=1.8 TeV collected by the CDF detector and includes data from both the W->e+nu and W->mu+nu decay channels. We fit the W boson transverse mass distribution to a set of templates from a Monte Carlo event generator and detector simulation in several ranges of the W transverse momentum. The measurement agrees with the Standard Model expectation, whereby the ratio of longitudinally to transversely polarized W bosons, in the Collins-Soper W rest frame, increases with the W transverse momentum at a rate of approximately 15% per 10 GeV/c.Comment: 47 pages, 16 figures, submitted to Physical Review

BaBar: sin(2beta) with Charmless and Radiative Decays

We present new measurements of time-dependent CP-violation parameters in hadronic penguin decays: B{sup 0} {yields} K{sup +}K{sup -}K{sub L}{sup 0}, K{sub S}{sup 0}{pi}{sup 0}{pi}{sup 0}, K{sub S}{sup 0}K{sub S}{sup 0}K{sub S}{sup 0}, {omega}K{sub L}{sup 0}, and a radiative penguin decay B{sup 0} {yields} K{sub S}{sup 0}{pi}{sup 0}{gamma} in a dataset of around 230 {center_dot} 10{sup 6} B{bar B} pairs collected by the BABAR detector at the asymmetric B Factory at SLAC. These CP asymmetry measurements probe for amplitudes beyond the Standard Model in loop-dominated decays of neutral B mesons. While we find a puzzling deviation of CP-asymmetry parameters from predicted values, a full confirmation still awaits more data

Search for lepton-number violating B[superscript +] → X[superscript −]ℓ[superscript +]ℓ[superscript ′+] decays

We report on a search for eleven lepton-number violating processes B[superscript +] → X[superscript −]ℓ[superscript +]ℓ[superscript '+] with X[superscript −] = K[superscript −], π[superscript −], ρ[superscript −], K[superscript *−], or D[superscript −] and ℓ[superscript +]/ℓ[superscript '+] = e[superscript +] or μ[superscript +], using a sample of 471±3 million B[¯ over B] events collected with the BABAR detector at the PEP-II e[superscript +]e[superscript −] collider at the SLAC National Accelerator Laboratory. We find no evidence for any of these modes and place 90% confidence level upper limits on their branching fractions in the range (1.5–26)×10[superscript −7].United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Observation of Time-Reversal Violation in the B[superscript 0] Meson System

Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B[superscript 0] or B̅[superscript 0]), and J/ψK[subscript L][superscript 0] or cc̅ K[subscript S][superscript 0] final states (referred to as B+ or B-), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B̅[superscript 0]→B[subscript -] and B_→B̅[superscript 0], as a function of the time difference between the two B decays. Using 468×10[superscript 6] BB̅ pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS[subscript T]+=-1.37±0.14(stat)±0.06(syst) and ΔS[subscript T[superscript]]-=1.17±0.18(stat)±0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation

Evidence for the Baryonic Decay [bar over B][superscript 0] → D[superscript 0]Λ[bar over Λ]

Evidence is presented for the baryonic B meson decay [bar over B][superscript 0] → D[superscript 0]Λ[bar over Λ] based on a data sample of 471 × 10[superscript 6] B[bar over B] pairs collected with the BABAR detector at the PEP-II asymmetric e[superscript +]e[superscript −] collider located at the SLAC National Accelerator Laboratory. The branching fraction is determined to be B([bar over B][superscript 0] → D[superscript 0]Λ[bar over Λ]) = (9.8[+2.9 over −2.6] ± 1.9) × 10[superscript −6], corresponding to a significance of 3.4 standard deviations including additive systematic uncertainties. A search for the related baryonic B meson decay [bar over B][superscript 0] → D[superscript 0]Σ[superscript 0][bar over Λ] with Σ[superscript 0] → Λγ is performed and an upper limit B([bar over B][superscript 0] → D[superscript 0]Σ[superscript 0][bar over Λ] + [bar over B][superscript 0] → D[superscript 0]Λ[bar over Σ][superscript 0]) < 3.1 × 10[superscript −5] is determined at 90% confidence level.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio