Evaluation of the LHCb RICH detectors and a measurement of the CKM angle γ\gamma

The future LHCb experiment at the Large Hadron Collider (LHC) at CERN will perform precision measurements of CP violation parameters in the neutral B systems. In this thesis the performance of the LHCb RICH system is evaluated, and the feasibility of a measurement of the CP violation parameter #gamma#, using the decays B_d"0 #-># D*"-#pi#"+, B_d"0 #-># D*"-#pi#"+ and their CP conjugates, is investigated. Efficient methods for the reconstruction of B_d"0 #-># D*"-#pi#"+ decays at LHCb are developed. Using the GEANT-based LHCb detector simulation program SICb, the reconstruction efficiencies and signal to background ratios are estimated. It is demonstrated that the decay channel B_d"0 #-># D*"-#pi#"+ can provide a precision in #gamma# of a few degrees after one year of LHCb data taking. A full-scale prototype of the LHCb RICH 2 detector has been tested in a testbeam at CERN in Summer 1998. It is shown to work according to expectation, in particular in the defining aspects of a RICH detector, the photon yield and the Cherenkov angle resolution. These results demonstrate that the LHCb RICH detectors are well understood and give confidence in the model of the RICH system used in the simulation studies for LHCb detector optimisation. In a testbeam in Summer 1999 a RICH prototype was tested using a 3x3 cluster of Multi-anode Photo Multiplier Tubes equipped with lenses. The tubes were read out within the LHC bunch-crossing interval of 25 ns for the first time. It is demonstrated that the MaPMT performs well and is a suitable photodetector for the LHCb RICH. (author)Available from British Library Document Supply Centre-DSC:D213936 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Monte Carlo Independent Lifetime Fitting at LHCb in Lifetime Biased Channels

Lifetime measurements at LHCb will help in detector calibration as well as providing constraints on lifetime differences in the $B_s$ system and other theoretical models. In order to exploit the full range of decays available in LHCb, it is important to have a method for fitting lifetimes in hadronic channels, which are biased by the impact parameter cuts in the trigger. We have investigated a Monte Carlo simulation independent method to take into account the trigger effects. The method is based on calculating event by event acceptance functions from the decay geometry and does not require any external input. This note presents current results with this method for both the full LHCb Monte Carlo for the channel $B^{0}_{d} \rightarrow D^{-} \pi^{+}$ and a toy Monte Carlo for the same channel, including a discussion of the expected statistical precision on lifetime measurements using this method once LHCb is operational

Amplitude analysis of four-body decays using a massively-parallel fitting framework

The GooFit Framework is designed to perform maximum-likelihood fits for arbitrary functions on various parallel back ends, for example a GPU. We present an extension to GooFit which adds the functionality to perform time-dependent amplitude analyses of pseudoscalar mesons decaying into four pseudoscalar final states. Benchmarks of this functionality show a significant performance increase when utilizing a GPU compared to a CPU. Furthermore, this extension is employed to study the sensitivity on the $D^0 - \bar{D}^0$ mixing parameters $x$ and $y$ in a time-dependent amplitude analysis of the decay $D^0 \rightarrow K^+\pi^-\pi^+\pi^-$. Studying a sample of 50 000 events and setting the central values to the world average of $x = (0.49 \pm0.15) \%$ and $y = (0.61 \pm0.08) \%$, the statistical sensitivities of $x$ and $y$ are determined to be $\sigma(x) = 0.019 \%$ and $\sigma(y) = 0.019 \%$.Comment: Proceedings of the 22nd International Conference on Computing in High Energy and Nuclear Physics, CHEP 201

A Monte Carlo simulation free method of measuring lifetimes using event-by-event acceptance functions at LHCb

A set of innovative methods and tools for precision lifetime and lifetime-difference measurements in hadronic B decays at LHCb is presented. All methods are purely data-driven and Monte Carlo simulation independent, a particularly important feature if lifetime measurements are to be made in the early period of LHCb's data taking. The methods and tools are shown to work in detailed simulation studies, including both Toy and Full Monte Carlo simulation studies of possible systematic biases in the measurements

LHCb's Potential to Measure Flavour-Specific CP-Asymmetry in Semileptonic and Hadronic Bs0B^0_s Decays

"The CP asymmetry in Bs-Bsbar mixing, denoted as a^s_{fs}, is sensitive to new weak phases in the presence of physics beyond the Standard Model. This can be probed through a measurement of the time-dependent charge asymmetry A^s_{fs}(t) in flavour-specific decays. This note describes the LHCb strategy to measure a^s_{fs} using a time-dependent method, in flavour untagged decays of Bs->Ds mu nu and Bs->Ds pi. We also investigate a measurement of the difference of a^s_{fs} and a^d_{fs} in Bs->Ds mu nu and Bd->Dmu nu decays which allows to control the systematic uncertainty that arise from detection asymmetries.

Search for rare and forbidden decays of charm and charmed-strange mesons to final states h^+- e^-+ e^+

We have searched for flavor-changing neutral current decays and lepton-number-violating decays of D^+ and D^+_s mesons to final states of the form h^+- e^-+ e^+, where h is either \pi or K. We use the complete samples of CLEO-c open-charm data, corresponding to integrated luminosities of 818 pb^-1 at the center-of-mass energy E_CM = 3.774 GeV containing 2.4 x 10^6 D^+D^- pairs and 602 pb^-1 at E_CM = 4.170 GeV containing 0.6 x 10^6 D^*+-_s D^-+_s pairs. No signal is observed in any channel, and we obtain 90% confidence level upper limits on branching fractions B(D^+ --> \pi^+ e^+ e^-) < 5.9 x 10^-6, B(D^+ --> \pi^- e^+ e^+) K^+ e^+ e^-) < 3.0 x 10^-6, B(D^+ --> K^- e^+ e^+) \pi^+ e^+ e^-) < 2.2 x 10^-5, B(D^+_s --> \pi^- e^+ e^+) K^+ e^+ e^-) < 5.2 x 10^-5, and B(D^+_s --> K^- e^+ e^+) < 1.7 x 10^-5.Comment: 9 pages, available through http://www.lns.cornell.edu/public/CLNS

Determination of the D0 -> K+pi- Relative Strong Phase Using Quantum-Correlated Measurements in e+e- -> D0 D0bar at CLEO

We exploit the quantum coherence between pair-produced D0 and D0bar in psi(3770) decays to study charm mixing, which is characterized by the parameters x and y, and to make a first determination of the relative strong phase \delta between doubly Cabibbo-suppressed D0 -> K+pi- and Cabibbo-favored D0bar -> K+pi-. We analyze a sample of 1.0 million D0D0bar pairs from 281 pb^-1 of e+e- collision data collected with the CLEO-c detector at E_cm = 3.77 GeV. By combining CLEO-c measurements with branching fraction input and time-integrated measurements of R_M = (x^2+y^2)/2 and R_{WS} = Gamma(D0 -> K+pi-)/Gamma(D0bar -> K+pi-) from other experiments, we find \cos\delta = 1.03 +0.31-0.17 +- 0.06, where the uncertainties are statistical and systematic, respectively. In addition, by further including external measurements of charm mixing parameters, we obtain an alternate measurement of \cos\delta = 1.10 +- 0.35 +- 0.07, as well as x\sin\delta = (4.4 +2.7-1.8 +- 2.9) x 10^-3 and \delta = 22 +11-12 +9-11 degrees.Comment: 37 pages, also available through http://www.lns.cornell.edu/public/CLNS/2007/. Incorporated referee's comment