CP Violation and Mixing in Multi-body DD decays

We present recent LHCb results and future prospects for CP violation and mixing measurements in multi-body charm decays. The complex amplitude structure of multi-body decays provides unique sensitivity to CP violation localised in certain phase space regions. A model-independent search in the phase space of D->pi+pi-pi+pi- and D->K+K-pi+pi- decays showed no evidence for localised CP violation. If one assumes the no CP violation hypothesis, the probability of getting the observed results is 9.1% and 41%, respectively. The model-independent determination of gamma from B->DK requires external input to account for the interference of D0 and D0bar amplitudes to the same final state. Previously this input could only be obtained at the charm threshold, but recently it has been proposed that D mixing can provide complimentary information. For the example of D->K+pi-pi+pi- decays, it is shown that charm mixing can be used to considerably improve current constraints on the coherence factor and average strong phase difference, with existing data.Comment: to appear in the proceedings of The 6th International Workshop on Charm Physics (CHARM 2013

Model-independent determination of the strong phase difference between D0D^0 and Dˉ0→π+π−π+π−\bar{D}^0 \to\pi^+\pi^-\pi^+\pi^- amplitudes

For the first time, the strong phase difference between $D^0$ and $\bar{D}^0\to\pi^+\pi^-\pi^+\pi^-$ amplitudes is determined in bins of the decay phase space. The measurement uses $818\,\mathrm{pb}^{-1}$ of $e^+e^-$ collision data that is taken at the $\psi(3770)$ resonance and collected by the CLEO-c experiment. The measurement is important for the determination of the $C P$-violating phase $\gamma$ in $B^{\pm}\to D K^{\pm}$ (and similar) decays , where the $D$ meson (which represents a superposition of $D^0$ and $\bar{D}^0$) subsequently decays to $\pi^+\pi^-\pi^+\pi^-$. To obtain optimal sensitivity to $\gamma$, the phase space of the $D \to \pi^+\pi^-\pi^+\pi^-$ decay is divided into bins based on a recent amplitude model of the decay. Although an amplitude model is used to define the bins, the measurements obtained are model-independent. The $CP$-even fraction of the $D \to \pi^+\pi^-\pi^+\pi^-$ decay is determined to be $F_{+}^{4\pi} = 0.769 \pm 0.021 \pm 0.010$, where the uncertainties are statistical and systematic, respectively. Using simulated $B^{\pm}\to D K^{\pm}, D \to \pi^+\pi^-\pi^+\pi^-$ decays, it is estimated that by the end of the current LHC run, the LHCb experiment could determine $\gamma$ from this decay mode with an uncertainty of $(\pm10\pm7)^\circ$, where the first uncertainty is statistical based on estimated LHCb event yields, and the second is due to the uncertainties on the parameters determined in this paper

TORCH: A Cherenkov Based Time-of-Flight Detector

TORCH is a novel high-precision time-of-flight detector suitable for large area applications and covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors. For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners. The development is divided into three phases. Phase 1 addresses the lifetime requirements for TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial tests show stable gain performance for integrated anode current >5 C/cm2 and a single photon time resolution of ≤ 30 ps. Initial simulations indicate the single photon timing resolution of the TORCH detector will be ∼70 ps

Analysis of the \Lambda_{b}\rar \Lambda \ell^+\ell^- decay in QCD

Taking into account the $\Lambda$ baryon distribution amplitudes and the most general form of the interpolating current of the $\Lambda_{b}$, the semileptonic \Lambda_{b}\rar \Lambda \ell^+\ell^- transition is investigated in the framework of the light cone QCD sum rules. Sum rules for all twelve form factors responsible for the \Lambda_{b}\rar \Lambda \ell^+\ell^- decay are constructed. The obtained results for the form factors are used to compute the branching fraction. A comparison of the obtained results with the existing predictions of the heavy quark effective theory is presented. The results of the branching ratio shows the detectability of this channel at the LHCb in the near future is quite high.Comment: 18 Pages, 2 Figures and 9 Table

The Magnetic Distortion Calibration System of the LHCb RICH1 Detector

The LHCb RICH1 detector uses hybrid photon detectors (HPDs) as its optical sensors. A calibration system has been constructed to provide corrections for distortions that are primarily due to external magnetic fields. We describe here the system design, construction, operation and performance.Comment: 9 pages, 14 figure

Beam tests of a large-scale TORCH time-of-flight demonstrator

The TORCH time-of-flight detector is designed to provide particle identification in the momentum range 2-10 GeV/c over large areas. The detector exploits prompt Cherenkov light produced by charged particles traversing a 10 mm thick quartz plate. The photons propagate via total internal reflection and are focused onto a detector plane comprising position-sensitive Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMT) detectors. The goal is to achieve a single-photon timing resolution of 70 ps, giving a timing precision of 15 ps per charged particle by combining the information from around 30 detected photons. The MCP-PMT detectors have been developed with a commercial partner (Photek Ltd, UK), leading to the delivery of a square tube of active area 53 $\times$ 53mm$^2$ with a granularity of 8 $\times$ 128 pixels equivalent. A large-scale demonstrator of TORCH, having a quartz plate of dimensions 660 $\times$ 1250 $\times$ 10 mm$^3$ and read out by a pair of MCP-PMTs with custom readout electronics, has been verified in a test beam campaign at the CERN PS. Preliminary results indicate that the required performance is close to being achieved. The anticipated performance of a full-scale TORCH detector at the LHCb experiment is presented.Comment: 12 pages, 7 figures, Paper submitted to Nuclear Instruments & Methods in Physics Research, Section A - Special Issue VCI 201

Exclusive Lambda_b -> Lambda l^+ l^- decay in two Higgs doublet model

Rare Lambda_b -> Lambda l^+ l^- decay is investigated in framework of general two Higgs doublet model, in which a new source of CP violation exists (model III). The polarization parameter, CP asymmetry and decay width are calculated. It is shown that CP asymmetry is a very sensitive tool for establishing model III.Comment: 16 pages, 3 figures, LaTeX formatte

Measurement of D*+/- diffractive cross sections in photoproduction at HERA

The first measurement of D*+/- meson diffractive photoproduction cross sections has been performed with the ZEUS detector at the HERA $ep$ collider, using an integrated luminosity of 38 pb^-1. The measurement has been performed for photon--proton center-of-mass energies in the range 130 < W < 280 GeV and photon virtualities Q^2 < 1 GeV^2. D*+/- mesons have been reconstructed with p_T(D*)>2 GeV and -1.5 D^0 \pi^+_s with D^0 --> K-\pi^+ (+c.c.). The diffractive component has been selected with 0.001<x_Pom<0.018. The measured diffractive cross section in this kinematic range is: \sigma_(ep --> e'D*Xp') = 0.74 +/- 0.21 (stat.)^{+0.27}_{-0.18} (syst.) +/-0.16 (p. diss.) ~nb (ZEUS preliminary). Measured integrated and differential cross sections have been compared to theoretical expectations.Comment: LaTeX2e, 10 pages, 6 Postscript figures. Talk given at the Russian Academy of Science (RAS) Nuclear Physics 2000 Conference, Moscow, Russia, November 27-December 2, 2000. To be published in Rus. Nucl. Phys. (Ya.F.), Proceedings of RAS Nucl. Phys. 2000 Con

The operation of a pressurized ultraviolet photoionization threshold cherenkov counter

We have successfully tested an ultraviolet photoionization Cherenkov counter in a 10 GeV/c pion beam. The counter has been tested to 11 atm pressure for use as a [pi]-K separator. The design and operation of the counter is described.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24311/1/0000577.pd