Measurement Of CP Violation Research Articles

B Physics in ATLAS

A brief overview of the ATLAS B physics programme is presented, including the trigger strategy, expectations for new physics searches in CP-violation measurements and rare b decays, and studies on the production mechanisms of b b ¯ pairs, doubly-heavy-flavoured hadrons and heavy quarkonium states.

CP-violations in B decays

Recent results on CP-violation measurements in B decays from energy-asymmetric B-factory experiments are reported. Thanks to large accumulated data samples, CP-violations in B decays in mixing-decay interference and direct CP-violation are now firmly established. The measurements of three angles of the unitarity triangle from CP-violations of B decays are quite consistent with the Standard Model expectations. These results strongly support the validity of the Kobayashi-Maskawa prescription of CP-violation.

LHCb Silicon Tracker Performance Studies

LHCb is one of the experiments for the Large Hadron Collider at CERN and is dedicated to B-physics and CP-violation measurements. To exploit its physics potential good tracking performance with high efficiency in a high particle density environment close to the beam pipe is required. Silicon strip detectors with large read-out pitch and long strips will be used for the LHCb Inner Tracker behind the magnet and the Trigger Tracker station in front of the magnet. We report here about the design of the Silicon Tracker, test beam results and the electrical tests foreseen during production

Design and performance of the LHCb silicon tracker

The LHCb detector is currently being installed at the large hadron collider at CERN and is foreseen to start operating in 2007. It is designed to perform high-precision measurements of CP violation and rare decays of B hadrons. The silicon tracker is part of the LHCb tracking system. It consists of the trigger tracker in front of the experiment's dipole magnet and the inner tracker downstream of the magnet. Both detectors employ silicon micro-strip technology to cope with the charged particle fluxes of up to 5 × 10 5 cm - 2 s - 1 that are expected in the innermost regions of the detectors. In this note, the design and production status of the trigger tracker and the inner tracker are presented together with an overview of the LHCb tracking strategy.

Software for the LHCb experiment

LHCb is an experiment for precision measurements of CP-violation and rare decays in B mesons at the LHC collider at CERN. The LHCb software development strategy follows an architecture-centric approach as a way of creating a resilient software framework that can withstand changes in requirements and technology over the expected long lifetime of the experiment. The software architecture, called GAUDI, supports event data processing applications that run in different processing environments ranging from the real-time high-level triggers in the online system to the final physics analysis performed by more than 100 physicists. The major architectural design choices and the arguments that lead to these choices will be outlined. Object oriented technologies have been used throughout. Initially developed for the LHCb experiment, GAUDI has been adopted and extended by other experiments. Several iterations of the GAUDI software framework have been released and are now being used routinely by the physicists of the LHCb collaboration to facilitate their development of data selection algorithms. The LHCb reconstruction (Brunel), the digitization (Boole) and analysis (DaVinci) applications together with the simulation application (Gauss), also based on Geant4, and event and detector visualization program (Panoramix) are all based on the GAUDI framework. All these applications are now in production.

Minimal archi-texture for neutrino mass matrices

The origin of the observed masses and mixing angles of quarks and leptons is one of imperative subjects in and beyond the standard model. Toward a deeper understanding of flavor structure, we investigate in this paper the minimality of fermion mass (Yukawa) matrices in unified theory. That is, the simplest matrix form is explored in light of the current experimental data for quarks and leptons, including the recent measurements of quark CP violation and neutrino oscillations. Two types of neutrino mass schemes are particularly analyzed; (i) Majorana masses of left-handed neutrinos with unspecified mechanism and (ii) Dirac and Majorana masses introducing three right-handed neutrinos. As a result, new classes of neutrino mass matrices are found to be consistent to the low-energy experimental data and high-energy unification hypothesis. For distinctive phenomenological implications of the minimal fermion mass textures, we discuss flavor-violating decay of charged leptons, the baryon asymmetry of the universe via thermal leptogenesis, neutrino-less double beta decay, and low-energy leptonic CP violation.

Recent Results from Belle experiment

The Belle experiment and KEKB asymmetric-energy e+e− collider has been successfully operated since 1999. The recent results from Belle experiment on the CP violation measurements, radiative and electroweak penguin decays, and new resonance observations are reported.

Direct CP violation and rare decays at BaBar

We present recent time integrated and time dependent measurements of Direct CP violation at the BaBar experiment.

Detection of magnetic helicity

Magnetic fields in various astrophysical settings may be helical and, in the cosmological context, may provide a measure of primordial CP violation during baryogenesis. Yet it is difficult, even in principle, to devise a scheme by which magnetic helicity may be detected, except in some very special systems. We propose that charged cosmic rays originating from known sources may be useful for this purpose. We show that the correlator of the arrival momenta of the cosmic rays is sensitive to the helicity of an intervening magnetic field. If the sources themselves are not known, the method may still be useful provided we have some knowledge of their spatial distribution.

Long term performance studies of the silicon strip detectors of the LHCb Silicon Tracker

LHCb is one of the experiments at the Large Hadron Collider at CERN. It is dedicated to B-physics and CP-violation measurements. To fully exploit its physics potential, a good tracking performance with high efficiency in the high particle density environment close to the beam pipe is required. For this purpose, the LHCb Silicon Tracker uses strip detectors with large read-out pitch and long strips. We give a summary of the R&D program of the Silicon Tracker and of performance studies for the long term operation in the LHC radiation environment.

Simulation of LHCb RICH detectors using GEANT4

LHCb is one of the experiments at the Large Hadron Collider at CERN. It aims to make precision measurements of CP violation in the B-meson decays. The detector simulation of LHCb was developed using the GEANT4 software toolkit interfaced to the LHCb software framework named GAUDI. This is now being used for a large production run of 210 million events. An important feature of the LHCb experiment is the use of Ring Imaging Cherenkov Counters (RICH) for particle identification. The Cherenkov photons created in this detector are focused onto an array of photodetectors made of Hybrid Photon Detectors. A brief overview of the GEANT4 based LHCb simulation program named GAUSS will be given with the main emphasis on RICH simulation and its verification.

RECENT RESULTS ON B DECAYS: Rare B Decay Highlights + Belle $b \to s\bar{q}q$ Time-dependent CPV

Highlights on recent experimental results on rare decays from asymmetric B-factories are reported. Also, the results on time-dependent CP violation measurements for decay modes where [Formula: see text] penguin diagram dominate from Belle are reported.

Improved measurement of CP-violation in $B \to (c{\bar c})K^{(\ast)0}$ decays

We present results on time-dependent CP asymmetries in neutral B decays. The amplitude of the CP asymmetry, sin 2β in the Standard Model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0or [Formula: see text] from its decay products. Using data collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure sin 2β = 0.722 ± 0.040( stat ) ± 0.023( syst ) and [Formula: see text], determining the sign of cos 2β to be positive at 86% CL.

SO(10) GUT's, Neutrinos and LFV

A model based on SO(10) × SU(2)F having symmetric mass textures with 5 zeros is constructed. The symmetric mass textures arising from the left-right symmetry breaking chain of SO (10) give rise to good predictions for the masses, mixing angles and CP violation measures in the quark and lepton sectors, all in agreement with the most up-to-date experimental data within 1 σ. Various lepton flavor violating decays in our model are also investigated. Unlike in models with lop-sided textures, our prediction for the decay rate of μ → e γ is much suppressed and yet it is large enough to be probed by the next generation of experiments. The observed baryonic asymmetry in the Universe can be accommodated utilizing soft leptogenesis.

Asymmetry and minimality of quark mass matrices

We systematically investigate general forms of mass matrices for three-generation up and down quarks, including asymmetrical ones in generation space. Viable zero matrix elements are explored which are compatible with the current observation of masses and mixing angles, and also with the recent measurement of CP violation in the B-meson system. The simplest form with the maximal number of vanishing matrix elements is found to be almost consistent with the experimental data, but has a scratch that one of the mixing angle is slightly large. At the next-to-minimal level, it is found with a help of leptonic generation mixing that only six patterns of mass matrices well describe the experimental data. These sets of mass textures predict all the properties of quarks, including the CP violation, as well as the large (charged) lepton mixing, which may be appropriate for the atmospheric neutrino in grand unification scheme.

The LHCb Silicon Tracker

LHCb is one of the experiments for the Large Hadron Collider at CERN, dedicated to B-physics and CP-violation measurements. To fully exploit the physics potential, a good tracking performance with high efficiency in a high particle density environment close to the beam pipe is required. Silicon strip detectors with large readout pitch and long strips will be used for the LHCb Inner Tracker after the magnet and the Trigger Tracker station in front of the magnet. The design of the Silicon Tracker in LHCb and corresponding test beam results are presented here.

The BTeV trigger—recent developments

BTeV is a collider experiment at the Fermilab Tevatron dedicated to precision measurements of CP violation, mixing and rare decays of beauty and charm hadrons. The detector is a forward spectrometer with a pixel vertex detector inside a dipole magnet. A unique feature of BTeV is the trigger, which reconstructs tracks and vertices in every beam crossing. We present here an overview of the BTeV trigger and a description of recent improvements in trigger timing.

From parameter space constraints to the precision determination of the leptonic Dirac CP phase

We discuss the precision determination of the leptonic Dirac CP phase $\delta_{CP}$ in neutrino oscillation experiments, where we apply the concept of ``CP coverage''. We demonstrate that this approach carries more information than a conventional CP violation measurement, since it also describes the exclusion of parameter regions. This will be very useful for next-generation long baseline experiments where for sizable $\sin^2 2 \theta_{13}$ first constraints on $\delta_{CP}$ can be obtained. As the most sophisticated experimental setup, we analyze neutrino factories, where we illustrate the major difficulties in their analysis. In addition, we compare their potential to the one of superbeam upgrades and next-generation experiments, which also includes a discussion of synergy effects. We find a strong dependence on the yet unknown true values of $\sin^2 2 \theta_{13}$ and $\delta_{CP}$, as well as a strong, non-Gaussian dependence on the confidence level. A systematic understanding of the complicated parameter dependence will be given. In addition, it is shown that comparisons of experiments and synergy discussions do in general not allow for an unbiased judgment if they are only performed at selected points in parameter space. Therefore, we present our results in dependence of the yet unknown true values of $\sin^2 2 \theta_{13}$ and $\delta_{CP}$. Finally we show that for $\delta_{CP}$ precision measurements there exist simple strategies including superbeams, reactor experiments, superbeam upgrades, and neutrino factories, where the crucial discriminator is $\sin^2 2 \theta_{13} \sim 10^{-2}$.

HIGHLIGHTS FROM FIVE YEARS AT THE B FACTORIES

The highlights and conflicts at the B factories are briefly reviewed. CP violation was established in 2001 in B0→J/ψKS and related modes, which has now become a precision measurement of CP violation in [Formula: see text] mixing. However, the situation for the B0→π+π- and charmless b→s modes, which also probe CP violation in the decay amplitude, are not quite settled yet. They could be hinting at the presence of both strong (CP conserving) and new physics (CP violating) phases. We critically assess the developments and discuss some related discrepancies and highlights, such as observation of direct CP violation, and make a projection towards the next few years.

CP violation and CKM measurements in Bottom and Charm decays at CDF

We present preliminary measurements of branching ratios and CP asymmetries in 5 charmless decay modes of the B mesons and precise measurement of direct CP asymmetry in Cabibbo-suppressed charm decays. We used 180pb−1 of the hadronic-b data stream of CDF's Tevatron Run2. The decay mode B s → ϕ ϕ has been observed for the first time, with a branching fraction of ( 1.4 ± 0.6 ± 0.2 ± 0.5 ) × 10 −5 . We also present the first measurement of the branching fraction B ( B s → K + K − ) = ( 3.56 ± 0.57 ± 0.50 ± 0.43 ) × 10 −5 .