arXiv subjects

T. Gershon

Publications and source records attributed to T. Gershon.

At least 37 records · Page 2Linked to original sources

arXiv2016

LHCSki 2016 - A First Discussion of 13 TeV Results

These are the proceedings of the LHCSki 2016 workshop "A First Discussion of 13 TeV Results" that has been held at the Obergurgl Universitätszentrum, Tirol, Austria, April 10 - 15, 2016. In this workshop the consequences of the most recent results from the LHC have been discussed, with a focus also on the interplay with dark matter physics, flavor physics, and precision measurements. Contributions from the workshop speakers have been compiled into this document.

hep-ph↗

arXiv2016

Model-independent determination of the strong-phase difference between D^0 and D^0-bar-> K^0_S,L h^+ h^- (h=pi,K) and its impact on the measurement of the CKM angle gamma/phi_3

We report the first determination of the relative strong-phase difference between D^0 -> K^0_S,L K^+ K^- and D^0-bar -> K^0_S,L K^+ K^-. In addition, we present updated measurements of the relative strong-phase difference between D^0 -> K^0_S,L pi^+ pi^- and D^0-bar -> K^0_S,L pi^+ pi^-. Both measurements exploit the quantum coherence between a pair of D^0 and D^0-bar mesons produced from psi(3770) decays. The strong-phase differences measured are important for determining the Cabibbo-Kobayashi-Maskawa angle gamma/phi_3 in B^- -> K^- D^0-tilde decays, where D^0-tilde is a D^0 or D^0-bar meson decaying to K^0_S h^+ h^- (h=pi,K), in a manner independent of the model assumed to describe the D^0 -> K^0_S h^+ h^- decay. Using our results, the uncertainty in gamma/phi_3 due to the error on the strong-phase difference is expected to be between 1.7 and 3.9 degrees for an analysis using B^- K^- D^0-tilde D^0-tilde -> K^0_S pi^+ pi^- decays, and between 3.2 and 3.9 degrees for an analysis based on B^- -> K^- D^0-tilde, D^0-tilde -> K^0_S K^+ K^- decays. A measurement is also presented of the CP-odd fraction, F_-, of the decay D^0 -> K^0_S K^+ K^- in the region of the phi -> K^+ K^- resonance. We find that in a region within 0.01 GeV^2/c^4 of the nominal phi mass squared F_- > 0.91 at the 90% confidence level.

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arXiv2015

Rare b hadron decays at the LHC

With the completion of Run~I of the CERN Large Hadron Collider, particle physics has entered a new era. The production of unprecedented numbers of heavy-flavoured hadrons in high energy proton-proton collisions allows detailed studies of flavour-changing processes. The increasingly precise measurements allow to probe the Standard Model with a new level of accuracy. Rare $b$ hadron decays provide some of the most promising approaches for such tests, since there are several observables which can be cleanly interpreted from a theoretical viewpoint. In this article, the status and prospects in this field are reviewed, with a focus on precision measurements and null tests.

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arXiv2015

Contributions to the width difference in the neutral $D$ system from hadronic decays

Recent studies of several multi-body $D^0$ meson decays have revealed that the final states are dominantly $CP$-even. However, the small value of the width difference between the two physical eigenstates of the $D^0$-$\overline{D}{}^0$ system indicates that the total widths of decays to $CP$-even and $CP$-odd final states should be the same to within about a percent. The known contributions to the width difference from hadronic $D^0$ decays are discussed, and it is shown that an apparent excess of quasi-$CP$-even modes is balanced, within current uncertainty, by interference effects in quasi-flavour-specific decays. Decay modes which may significantly affect the picture with improved measurements are considered.

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arXiv2015

Heavy Flavour Physics at the LHC

A summary of results in heavy flavour physics from Run 1 of the LHC is presented. Topics discussed include spectroscopy, mixing, CP violation and rare decays of charmed and beauty hadrons.

hep-ex↗

arXiv2015

First determination of the $CP$ content of $D \to π^+π^-π^+π^-$ and updated determination of the $CP$ contents of $D \to π^+π^-π^0$ and $D \to K^+K^-π^0$

Quantum-correlated $ψ(3770) \to D\bar{D}$ decays collected by the CLEO-c experiment are used to perform a first measurement of $F_+^{4π}$, the fractional $CP$-even content of the self-conjugate decay $D \to π^+π^-π^+π^-$, obtaining a value of $0.737 \pm 0.028$. An important input to the measurement comes from the use of $D \to K^0_{\rm S}π^+π^-$ and $D \to K^0_{\rm L}π^+π^-$ decays to tag the signal mode. This same technique is applied to the channels $D \toπ^+π^-π^0$ and $D \to K^+K^-π^0$, yielding $F_+^{πππ^0} = 1.014 \pm 0.045 \pm 0.022$ and $F_+^{KKπ^0} = 0.734 \pm 0.106 \pm 0.054$, where the first uncertainty is statistical and the second systematic. These measurements are consistent with those of an earlier analysis, based on $CP$-eigenstate tags, and can be combined to give values of $F_+^{πππ^0} = 0.973 \pm 0.017$ and $F_+^{KKπ^0} = 0.732 \pm 0.055$. The results will enable the three modes to be included in a model-independent manner in measurements of the unitarity triangle angle $γ$ using $B^\mp \to DK^\mp$ decays, and in time-dependent studies of $CP$ violation and mixing in the $D\bar{D}$ system.

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arXiv2014

Averages of $b$-hadron, $c$-hadron, and $τ$-lepton properties as of summer 2014

This article reports world averages of measurements of $b$-hadron, $c$-hadron, and $τ$-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available through summer 2014. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, $CP$ violation parameters, parameters of semileptonic decays and CKM matrix elements.

hep-ex↗

arXiv2014

First determination of the CP content of D->pi+pi-pi0 and D->K+K-pi0

Quantum-correlated psi(3770)->DDbar decays collected by the CLEO-c experiment are used to perform first measurements of F+, the fractional CP-even content of the self-conjugate decays D->pi+pi-pi0 and D->K+K-pi0. Values of 0.968 +/- 0.017 +/- 0.006 and 0.731 +/- 0.058 +/- 0.021 are obtained for pi+pi-pi0 and K+K-pi0, respectively. It is demonstrated how modes of this sort can be cleanly included in measurements of the unitarity triangle angle gamma using B+/- -> D K+/- decays. The high CP-even content of D -> pi+pi-pi0, in particular, makes this a promising mode for improving the precision on gamma.

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arXiv2014

Performance of the LHCb Vertex Locator

The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7 mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 microns is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n+-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 micron for translations in the plane transverse to the beam. A primary vertex resolution of 13 microns in the transverse plane and 71 microns along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 microns is achieved for particles with transverse momentum greater than 1 GeV/c.

physics.ins-det↗

arXiv2014

New determination of the D0->K-pi+pi0 and D0->K-pi+pi+pi- coherence factors and average strong-phase differences

Measurements of the coherence factors (R_Kpipi0 and R_K3pi) and the average strong-phase differences (delta^Kpipi0_D and delta^K3pi_D) for the decays D0-> K-pi+pi0 and D0->K-pi+pi+pi- are presented. These parameters are important inputs to the determination of the unitarity triangle angle gamma in B+/- -> DK+/- decays, where D designates a D0 or D0bar meson decaying to a common final state. The measurements are made using quantum correlated DDbar decays collected by the CLEO-c experiment at the psi(3770) resonance, and augment a previously published analysis by the inclusion of new events in which the signal decay is tagged by the mode D-> K0Spi+pi-. The measurements also benefit from improved knowledge of external inputs, namely the D0D0bar mixing parameters, r_D^Kpi and several D-meson branching fractions. The measured values are R_Kpipi0 = 0.82 +- 0.07, delta_D^Kpipi0 = (164+20-14) deg., R_K3pi = 0.32+0.20-0.28 and delta^K3pi_D = (225+21_-78) deg. Consideration is given to how these measurements can be improved further by using the larger quantum-correlated data set collected by BESIII.

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arXiv2013

Report of the Quark Flavor Physics Working Group

This report represents the response of the Intensity Frontier Quark Flavor Physics Working Group to the Snowmass charge. We summarize the current status of quark flavor physics and identify many exciting future opportunities for studying the properties of strange, charm, and bottom quarks. The ability of these studies to reveal the effects of new physics at high mass scales make them an essential ingredient in a well-balanced experimental particle physics program.

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arXiv2013

Radiation damage in the LHCb Vertex Locator

The LHCb Vertex Locator (VELO) is a silicon strip detector designed to reconstruct charged particle trajectories and vertices produced at the LHCb interaction region. During the first two years of data collection, the 84 VELO sensors have been exposed to a range of fluences up to a maximum value of approximately $\rm{45 \times 10^{12}\,1\,MeV}$ neutron equivalent ($\rm{1\,MeV\,n_{eq}}$). At the operational sensor temperature of approximately $-7\,^{\circ}\rm{C}$, the average rate of sensor current increase is $18\,\upmu\rm{A}$ per $\rm{fb^{-1}}$, in excellent agreement with predictions. The silicon effective bandgap has been determined using current versus temperature scan data after irradiation, with an average value of $E_{g}=1.16\pm0.03\pm0.04\,\rm{eV}$ obtained. The first observation of n-on-n sensor type inversion at the LHC has been made, occurring at a fluence of around $15 \times 10 ^{12}$ of $1\,\rm{MeV\,n_{eq}}$. The only n-on-p sensors in use at the LHC have also been studied. With an initial fluence of approximately $\rm{3 \times 10^{12}\,1\,MeV\,n_{eq}}$, a decrease in the Effective Depletion Voltage (EDV) of around 25\,V is observed, attributed to oxygen induced removal of boron interstitial sites. Following this initial decrease, the EDV increases at a comparable rate to the type inverted n-on-n type sensors, with rates of $(1.43\pm 0.16) \times 10 ^{-12}\,\rm{V} / \, 1 \, \rm{MeV\,n_{eq}}$ and $(1.35\pm 0.25) \times 10 ^{-12}\,\rm{V} / \, 1 \, \rm{MeV\,n_{eq}}$ measured for n-on-p and n-on-n type sensors, respectively. A reduction in the charge collection efficiency due to an unexpected effect involving the second metal layer readout lines is observed.

physics.ins-det↗

arXiv2012

Amplitude analysis of D0->K+K-pi+pi-

The first flavor-tagged amplitude analysis of the decay D0 to the self-conjugate final state K+K-pi+pi- is presented. Data from the CLEO II.V, CLEO III, and CLEO-c detectors are used, from which around 3000 signal decays are selected. The three most significant amplitudes, which contribute to the model that best fits the data, are phirho0, K1(1270)+-K-+, and non-resonant K+K-pi+pi-. Separate amplitude analyses of D0 and D0-bar candidates indicate no CP violation among the amplitudes at the level of 5% to 30% depending on the mode. In addition, the sensitivity to the CP-violating parameter gamma/phi3 of a sample of 2000 B+ -> D0-tilde(K+K-pi+pi-)K+ decays, where D0-tilde is a D0 or D0-bar, collected at LHCb or a future flavor facility, is estimated to be (11.3 +/- 0.3) degrees using the favored model.

hep-ex↗

arXiv2010

Physics at Super B Factory

This report presents the results of studies that investigate the physics reach at a Super $B$ factory, an asymmetric-energy $e^+e^-$ collider with a design luminosity of $8 \times 10^{35}$ cm$^{-2}$s$^{-1}$, which is around 50 times as large as the peak luminosity achieved by the KEKB collider. The studies focus on flavor physics and CP violation measurements that could be carried out in the LHC era. The physics motivation, key observables, measurement methods and expected precisions are presented.

hep-ex↗

arXiv2009

Averages of b-hadron and c-hadron Properties at the End of 2007

This article reports world averages for measurements of b-hadron and c-hadron properties obtained by the Heavy Flavor Averaging Group (HFAG) using the results available at the end of 2007. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, and parameters of semileptonic decays.

hep-ex↗

arXiv2008

Proceedings of SuperB Workshop VI: New Physics at the Super Flavor Factory

The sixth SuperB Workshop was convened in response to questions posed by the INFN Review Committee, evaluating the SuperB project at the request of INFN. The working groups addressed the capability of a high-luminosity flavor factory that can gather a data sample of 50 to 75 /ab in five years to elucidate New Physics phenomena unearthed at the LHC. This report summarizes the results of the Workshop.

hep-ph↗

arXiv2008

B, D and K decays

With the advent of the LHC, we will be able to probe New Physics (NP) up to energy scales almost one order of magnitude larger than it has been possible with present accelerator facilities. While direct detection of new particles will be the main avenue to establish the presence of NP at the LHC, indirect searches will provide precious complementary information, since most probably it will not be possible to measure the full spectrum of new particles and their couplings through direct production. In particular, precision measurements and computations in the realm of flavour physics are expected to play a key role in constraining the unknown parameters of the Lagrangian of any NP model emerging from direct searches at the LHC. The aim of Working Group 2 was twofold: on one hand, to provide a coherent, up-to-date picture of the status of flavour physics before the start of the LHC; on the other hand, to initiate activities on the path towards integrating information on NP from high-pT and flavour data.

hep-ph↗

arXiv2007

On the Physics Case of a Super Flavour Factory

We summarize the physics case of a high-luminosity e+e- flavour factory collecting an integrated luminosity of 50-75 ab^(-1). Many New Physics sensitive measurements involving B and D mesons and tau leptons, unique to a Super Flavour Factory, can be performed with excellent sensitivity to new particles with masses up to ~100 (or even ~1000 TeV). Flavour- and CP-violating couplings of new particles that may be discovered at the LHC can be measured in most scenarios, even in unfavourable cases assuming minimal flavour violation. Together with the LHC, a Super Flavour Factory, following either the SuperKEKB or the SuperB proposal, could be soon starting the project of reconstructing the New Physics Lagrangian.

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