abstract

We present recent results on \(B\) physics from the Belle detector at the KEKB asymmetric \(e^+e^-\) collider. The mixing-induced \(CP\) violation parameter is measured to be \(\sin 2\phi _1 = 0.58 ^{+0.32}_{-0.34} ({\rm stat}.) ^{+0.09}_{-0.10} ({\rm syst}.)\) based on a data sample of 10.5 fb\(^{-1}\) at the \({\mit \Upsilon }(4S)\) resonance. Other topics including \(B\)–\(\bar {B}\) mixing, observations of rare decays, and \(|V_{cb}|\) measurements are also reported.

abstract

We present a summary of 1999–2000 BaBar results from BaBar corresponding to about 8–9 fb\(^{-1}\) of integrated luminosity. All the numbers given in this writeup are preliminary. We report on measurements of \(B\) meson lifetime, \(B^0 \overline B^0\) mixing, \(\sin 2\beta \) of the CKM triangle, and branching ratios of some charmless \(B\) decays.

abstract

The CLEO detector at the Cornell Electron-Positron Storage Ring is used for the study of the properties and interactions of the \(b\) and \(c\) quarks and the \(\tau \) lepton. I will review recent CLEO data on \(b\) physics with special relevance to \(CP\) violation: \(B\)-meson decays through radiative and gluonic penguin amplitudes and the effects on branching ratios and charge asymmetries of interference between penguin and tree amplitudes in two-body charmless \(B\) decays.

abstract

A summary of important LEP measurements in the \(b\)-quark physics is presented. The following topics are reviewed: \(b\)-fragmentation, the spectroscopy and lifetimes of beauty hadrons, \(B^0\)–\({\overline {B}}^0\) oscillations and the extraction of the Cabibbo–Kobayashi–Maskawa (CKM) matrix elements \(\left | V_{cb} \right |\) and \(\left | V_{ub} \right |\).

abstract

Searches for the Standard Model Higgs and SUSY Higgses have been performed in the data collected by the four LEP experiments ALEPH, DELPHI, L3 and OPAL in the year 2000 at a centre-of-mass energies between 200 and 209 GeV corresponding to a total integrated luminosity of around 220 pb\(^{-1}\) per experiment. An excess of data above background predictions indicates a possible production of a Higgs boson with mass in the vicinity of 115 GeV/\(c^2\).

abstract

The preliminary results of charged trilinear gauge boson \(WWV,~V\equiv Z\)/\(\gamma \) coupling values presented in this paper were obtained by the four LEP2 experiments ALEPH, DELPHI, L3 and OPAL by analysing the data collected at LEP energies ranging from \(\sqrt {s}=183\) GeV to \(\sqrt {s}=202\) GeV. At these energies, significantly above the kinematic threshold for \(W^+W^-\) boson pair production, each of the four experiments collected data equivalent to more than \(\mathcal {L} \sim 500~{\rm pb}^{-1}\) of integrated luminosity. The estimation of trilinear gauge boson couplings based on this data provides an independent check of the gauge nature of the Standard Model.

abstract

The CDF collaboration has adapted several heavy flavor tagging techniques and employed them in analyses of time-dependent flavor asymmetries using data from the Tevatron Run I. The tagging algorithms were calibrated using low-\(p_{\rm T}\) inclusive lepton and dilepton trigger data samples. The tagging techniques were applied to a sample of \(\sim 400\) \(B_d^0\)/\(\overline {B}_d{^0} \rightarrow J\)/\(\psi K^0_{\rm S}\) decays and were used to measure the CP violation parameter, \(\sin (2\beta )\). Prospects for future improved measurements of the \(CP\) violation parameters at the Tevatron are briefly discussed.

abstract

A new technique to measure the \(b\) quark fragmentation fractions in \(p \overline {p}\) collisions is described. Using a 70 pb\(^{-1}\) sample of low-mass dimuon trigger data recorded with the Collider Detector at Fermilab, we identify \(B\) mesons by observing double semileptonic decays \(b \rightarrow c \mu X\) with \(c \rightarrow s \mu X\). By counting the numbers of \(K^{\ast }(892)^0\), \(K^{\ast }(892)^+\) and \(\phi (1020)\) mesons produced in association with these muon pairs, we measure the ratio of strange to non-strange \(B\) meson production to be \(f_s\)/\((f_u + f_d) = (21.0 \pm 3.6 {\rm (stat.)}^{+ 3.8}_{- 3.0} {\rm (syst.)})\%\). This measurement and the complementary measurement done at CDF are the most precise available from hadron collisions to date. The combined CDF result on the absolute fragmentation fraction for \(B^0_s\) mesons is \(f_s = (16.0 \pm 2.5)\%\).

abstract

The LHCb experiment at the Large Hadron Collider (LHC) at CERN is designed to study \(CP\)-violation and rare decays in the \(B\)-meson system. A general overview of the project is given, including the physics motivation, the design of the detector and the expected LHCb performance.

abstract

The main focus of ATLAS \(b\) physics has traditionally been on the standard model. In the last few years also the aspects of new physics in \(B\)-decays has been addressed. Another new field of studies started recently is a beauty production. We give an overview of the older as well as more recent results. After an introduction outlining selected trigger and detector performance characteristics, we explain methods and goals of \(CP\) violation measurements in decay channels of \(B_d^0\) meson, physics of \(B_s^0\) system and of rare decays. Finally, the ATLAS program for beauty production measurements is presented.

abstract

HERA-B is a fixed target experiment using the 920 GeV proton beam of the HERA collider at DESY in Hamburg. The experiment was proposed in 1994 with as a primary goal the measurement of \(CP\) violation in the \(B\) system, especially in the gold plated decay \(B^0\to J\)/\(\psi K^0_{\rm S}\). Meanwhile, the HERA-B detector is essentially completed. We report on the status of the detector, first physics results and the physics program for the next years.

abstract

I discuss a novel method to study the indirect violation of the discrete symmetries \(CP\), \(T\) and \(CPT\) in the \(B_{d}\)-system. It is based on the opportunity offered by \(B\)-factories to tag the \(CP\) eigenstate of \(B_{d}\) by means of the \(CP\) Conserving Direction. Transitions between both flavour and \(CP\) tagged states are used to construct genuine and non-genuine \(CP\)-odd, \(T\)-odd and \(CPT\)-odd asymmetries.

abstract

I review the theoretical foundations of QCD Factorization in nonleptonic \(B\)-Decays. This approach, developed in collaboration with Martin Beneke, Gerhard Buchalla and Matthias Neubert, provides a rigorous framework for the analysis of these decays in the heavy-quark limit. The significance of power corrections, terms which are formally suppressed by powers of \({\mit \Lambda }_{\rm QCD}\)/\(m_b\) and which are not calculable in perturbation theory but which may have a significant impact on phenomenologically important decays, is discussed.

abstract

In the perturbative QCD approach to exclusive \(B\) decays to two light mesons, the leading twist contribution corresponds to those diagrams in the Lepage–Brodsky expansion in which the would be spectator quark receives its recoil momentum via one gluon exchange. We show that the resulting amplitude, which in the spectator model is real, acquires an imaginary part which may be comparable in size to its real part. Thus, this source of the strong interaction phase in the amplitude must be taken into account in general to discuss, reliably, the expectations for \(CP\) violation in \(B\) decays at any B-factory type scenario.

abstract

Inelastic rescatterring effects in \(B\) decays into a pair \(PP\) of pseudoscalar mesons (\(PP = \pi \pi \) or \(K\overline {K}\)) are discussed. It is assumed that \(B\) meson decays through a short-distance tree-diagram process into two jet-like states composed of low-mass resonances \(M_1M_2\) which rescatter into \(PP\). The rescatterring of resonance pair \(M_1 M_2\) into the final \(PP\) state is assumed to proceed through a Regge flavour exchange. Since such processes constitute a fraction, diminishing with increasing energy, of total inelastic \(PP\) scattering, the inelastic rescattering contribution should die out for \(m_B \to \infty \). At \(m_B = 5.2\,\)GeV, however, explicit estimates show that rescattering corrections could be substantial, leading to long-distance corrections to \(B^0 \to K\overline {K}\), comparable to short-distance penguin contributions.

abstract

The heavy mass expansion has become a standard tool that has significantly evolved since its formulation about thirteen years ago. Some of the major results of the heavy mass expansion, namely the determination of \(V_{cb}\) (both exclusive and inclusive) and lifetime calculations, are reviewed and some open problems are pointed out.

abstract

Inspecting limits on \(|V_{ub}|\) estimates, great need is seen for improvement. One method to determine the related \(|V_{ub}\)/\(V_{cb}|\) ratio is proposed. We take into account first-order perturbative and non-perturbative leading-twist QCD corrections. We analyze in detail the impact of model uncertainties on the accuracy of our prediction.

abstract

The status of theoretical calculations of BR\([\bar {B} \to X_s \gamma ]\) is discussed. It is pointed out that replacing \(m_c^{\rm pole}/m_b^{\rm pole}\) in the matrix element \(\langle {X_s \gamma | (\bar {s}c)_{\scriptscriptstyle V-A}(\bar {c}b)_ {\scriptscriptstyle V-A} | b\rangle }\) by the more appropriate \(m_c^{\overline {\rm MS}}(\mu )/m_b^{\rm pole}\) with \(\mu \in [m_c,m_b]\) causes an 11% enhancement of the SM prediction for the branching ratio, and has a sizeable effect on the uncertainty. However, the uncertainty can be maintained at the level of around 10% thanks to an observation that \(m_b(\mu )\) in the top-quark contribution to the decay amplitude is the main source of perturbative QCD effects in the considered process.

abstract

Using the effective Lagrangian approach we compute the dominant for \(\tan \beta \gg 1\) supersymmetric contributions to the leptonic decay rates of \(B^0_{d,s}\) mesons. We point out that in this limit the \(CP\) violating asymmetries measured in the decays \(B^0_d(\bar B^0_d)\rightarrow \tau ^-\tau ^+\) can be interesting probes of the complex phases of the MSSM parameters and/or the \(V_{td}\) element of the CKM matrix.

abstract

A solution to the supersymmetric flavour and \(CP\) problems in which the first two generations of sfermions are heavier than a few TeV and approximately degenerate in mass is re-considered from a cosmological perspective. It is shown that if the lightest supersymmetric particle is essentially bino-like then requiring that all flavour changing neutral current and \(CP\)-violating processes are adequately suppressed, imposes severe limits on the bino mass, typically \(m_{\,\widetilde {B}}\gtrsim (200\)–300) GeV. This leads to difficulties for models implementing the scenario of heavy sfermion masses.

abstract

We consider a general two-Higgs-doublet model with \(CP\) violation in the scalar sector, that leads, at the one-loop level of the perturbation expansion, to \(CP\) violation in the process \({e^+e^-} \to {t\bar {t}} \to l^ \pm \dots \) and \({e^+e^-} \to {t\bar {t}} \to {\stackrel {{\scriptscriptstyle (-)}}{b}} \dots \). The goal of this study is to include consistently \(CP\)-violating effects in distributions of top-quark decay products (\(l^\pm \) or \({\stackrel {{\scriptscriptstyle (-)}}{b}} \)) that emerge both from \({t\bar {t}}\) production and from \(t\) or \(\bar {t}\) decay processes.

abstract

Neutrino flavors, light and heavy, are discussed in their interdependence within the minimal unifying gauge group of SO10. The general situation which excludes the existence of an exact symmetry from which exactly vanishing light neutrino masses would follow is discussed. Subtle and simple consequences for ‘low–low’ oscillation phenomena are presented in a general framework.

abstract

The CPLEAR experiment measures \(CP\)-, \(T\)-, and \(CPT\)-symmetries in the neutral kaon system. For the first time, \(T\)-violation and \(CPT\)-conservation is measured by a direct method using semileptonic decays. The limit on the \(CPT\)-violation parameter Re \((\delta )\) is improved by two orders of magnitude as compared to previous measurements. An indirect test of \(CPT\) symmetry is performed using the Bell–Steinberger relation and CPLEAR results, improving the current limits on Re \((\varepsilon )\) and Im \((\delta )\) by almost one order of magnitude.

abstract

The main goal of the NA48 experiment at the CERN SPS accelerator is the measurement of the direct \(CP\) violation parameter Re\((\varepsilon '/\varepsilon )\) in the \(K^0 \rightarrow 2\pi \) decays, with an accuracy close to \(2\times 10^{-4}\). The preliminary result obtained from 1998 data is reviewed. The use of intense \(K^0_{\rm S}\) and \(K^0_{\rm L}\) beams allows in parallel the investigation of rare \(CP\) violating decays. The future project aiming to study direct \(CP\) violation with charged kaon beams is briefly discussed.

abstract

Recent results obtained by the NA48 Collaboration on rare \({K_{\rm S}}\) decays and future prospects are presented.

abstract

NA48 has searched for rare neutral kaon decays in data collected in 1998 and 1999. These searches were performed with simultaneous \({K_{\rm L}}\) and \({K_{\rm S}}\) beams during the \(\mathrm {\varepsilon }\)’/\(\mathrm {\varepsilon }\) programme. Preliminary results for the decays \({K_{\rm L}\rightarrow \pi ^0 \gamma \gamma }\), \({K_{\rm L} \rightarrow e^+e^-e^+e^-}\) and \({K_{\rm L} \rightarrow \mu ^+\mu ^-e^+e^-}\) are presented.

abstract

The status of the KLOE experiment at the DA\(\Phi \)NE facility is presented. The detector on-beam performances are discussed. Methods for the selection and analysis of the relevant \(K^{0}_{\rm L}K^{0}_{\rm S}\) decay channels have been developed and optimized with the data collected so far. A summary of preliminary results is given. Analysis of the collected statistics in year 2000 is in progress. The perspectives of the next data taking campaign are also presented.