17667065
Review of Charm Semileptonic Decays and QCD
In this paper, we review recent progress in the field of semileptonic decays of charm mesons, including topics on the relative branching ratio and the form factors. The comparison between the experimental form factor measurements and the Lattice QCD calculations is emphasized.
119679827
RECENT FOCUS RESULTS ON CHARM MIXING
We present the recent result on CP mixing based on a high statistics photoproduced charm sample collected by the FOCUS experiment. We compare the lifetimes of two neutral D meson decays: D0→K- π+ and D0→K-K+. A mixing parameter for the neutral D system (yCP) is obtained under the assumption that K-π+ is an equal mixture of CP odd and even eigenstates.
5633838
Recent Results on CP Lifetime Differences of Neutral D Mesons
The mixing parameter y_cp for the neutral D system can be obtained by comparing the lifetimes of CP eigenstate decays of the D mesons. Recent results on the lifetime differences from the Belle, CLEO, FOCUS(E831) experiments are summarized in this article. The neutral D decay modes analyzed by the experiments are: The D0->Kpi mode with the assumption that it is an equal mixture of CP even and odd eigenstates, and the CP even modes D0->KK and D0->pipi.
118421849
Tau physics from LEP
We briefly review recent analysis on the tau lepton by four LEP experiments, ALEPH, DELPHI, L3 and OPAL, based on data samples generated at the Z peak. Intrinsic properties of the tau lepton as well as applications to various physics topics are treated from an experimental point of view. The summarized analysis subjects include lifetime, leptonic branching ratios, hadronic decay structures, dipole moments, related electroweak and QCD properties, and the mass of the tau neutrino.
118099621
A measurement of the polarization asymmetry of the tau lepton using the L3 detector at LEP
With a data sample of e e events collected in the L detector at LEP during we did a measurement of the polarization of leptons as a function of the production polar angle with respect to the incident e beam direction We used the following prong decay channels e e and a As the result we obtained the asymmetries A and Ae Combining this with the previous data measurement by L we ob tained A and Ae These asymmetries gave the ratio of vector to axial vector weak neutral coupling con stants for electrons as g V g e A and for taus as g V g A The numbers are consistent with the hypothesis of e lepton universality Assuming the e neutral current universality the e ective electroweak mixing angle is calculated as sin e w Advisor Professor Aihud Pevsner
119805142
Recent FOCUS results on charm mixing and CP violation
We summarize recent results on CP violation and mixing based on a high statistics photo-produced charm sample collected by the FOCUS experiment. We compare the lifetimes of two neutral D meson decays: D0 → K−π+ and D0 → K−K+. A mixing parameter for the neutral D system (yCP) is obtained under the assumption that K−π+ is an equal mixture of CP odd and even eigenstates. In addition, we searched for a CP width asymmetry in D+ → K−K+π+, D0 → K−K+ and D0 → π−π+. We found no evidence for CP violation by comparing the decay rates for the particle and antiparticle.
59435944
UsingMT2to distinguish dark matter stabilization symmetries
We examine the potential of using colliders to distinguish models with parity (Z_2) stabilized dark matter (DM) from models in which the DM is stabilized by other symmetries, taking the latter to be a Z_3 symmetry for illustration. The key observation is that a heavier mother particle charged under a Z_3 stabilization symmetry can decay into one or two DM particles along with Standard Model (SM) particles. This can be contrasted with the decay of a mother particle charged under a parity symmetry; typically, only one DM particle appears in the decay chain. In arXiv:1003.0899, some of us studied the distributions of visible invariant mass from the decay of a single such mother particle in order to highlight the resulting distinctive signatures of Z_3 symmetry versus parity symmetry stabilized dark matter candidates. We now describe a complementary study which focuses on decay chains of the two mother particles which are necessarily present in these events. We also include in our analyss the missing energy/momentum in the event. For the Z_3 symmetry stabilized mothers, the resulting inclusive final state can have two, three or four DM particles. In contrast, models with Z_2 symmetry can have only two. We show that the shapes and edges of the distribution of M_T2-type variables, along with ratio of the visible momentum/energy on the two sides of the event, are powerful in distinguishing these different scenarios.
118600637
Regularization parameters for the self-force of a scalar particle in a general orbit about a Schwarzschild black hole
The interaction of a charged particle with its own field results in the "self-force" on the particle, which includes but is more general than the radiation reaction force. In the vicinity of the particle in curved spacetime, one may follow Dirac and split the retarded field of the particle into two parts, (1) the singular source field, \sim q/r, and (2) the regular remainder field. The singular source field exerts no force on the particle, and the self-force is entirely caused by the regular remainder. We describe an elementary multipole decomposition of the singular source field which allows for the calculation of the self-force on a scalar-charged particle orbiting a Schwarzschild black hole.
118595793
Bayesian naturalness of the CMSSM and CNMSSM
The recent discovery of the 125.5 GeV Higgs boson at the LHC has fueled interest in the next-to-minimal supersymmetric standard model (NMSSM) as it may require less fine-tuning than the minimal model to accommodate such a heavy Higgs. To this end we present Bayesian naturalness priors to quantify fine-tuning in the (N)MSSM. These priors arise automatically as Occam razors in Bayesian model comparison and generalize the conventional Barbieri-Giudice measure. In this paper we show that the naturalness priors capture features of both the Barbieri-Giudice fine-tuning measure and a simple ratio measure that has been used in the literature. We also show that according to the naturalness prior the constrained version of the NMSSM is less tuned than the CMSSM.
117044003
Parity violation in electron scattering from carbon: A progress report
An experiment is being performed at the MIT Bates Linear Accelerator Center to measure the parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons from Carbon. The asymmetry, which is due to the isoscalar component of the neutral weak current, is predicted to be about 0.6{times}10{sup {minus}6}. We have recently obtained preliminary data with polarized electrons. The status of the experiment is discussed.
121056144
Operation of the LAMPF stopped muon channel for small gas targets
Abstract We describe the operation of the LAMPF stopped muon channel (SMC) in a mode that provides a small beam spot and a narrow momentum spread suitable for stopping negative muons in presently available optically pumped spin-exchange polarized gas targets. This technique is expected to be useful for the production of polarized muonic atoms. Monte Carlo studies of the channel are discussed, and we describe experimental results including measurements of the fraction of negative muon stops in a 6 cm 3 krypton target at 1 atm as a function of beam momentum.