Regular Series

Vol. 43 (2012), No. 7, pp. 1383 – 1660

Cracow Epiphany Conference Present and Future of B Physics

Study of the \(B^{-} \to D_s^{(\star )+} K^{-} \ell ^{-} {\overline \nu }_{\ell }\) Decays at Belle

Acta Phys. Pol. B 43, 1391 (2012)

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Preliminary results containing measurements of the decays \(B^{-} \to D_s^{(\star )+} K^{-} \ell ^{-} \overline {{\nu }}_{\ell }\) are presented (the inclusion of the charge-conjugate modes is implied). Analysis is based on data sample of 656 \(B\overline {B}\) collected at Belle detector in the clean environment of KEKB asymmetric-energy \(e^{+}e^{-}\) collider. Combined \(B \to D_s^{(*)} K \ell \nu _{\ell }\) modes were observed with significance of \(6\sigma \). First time these modes were measured separately: \(\mathcal {B}(B\to D_s K \ell \nu _{\ell }) =[3.0 \pm 1.2 ({\rm stat}){}^{+1.1}_{-0.8}({\rm syst})] \times 10^{-4}\) (\(3.4 \sigma \), first evidence), \(\mathcal {B}(B\to D_s^{*} K \ell \nu _{\ell }) \lt 5.4 \times 10^{-4}~{\rm C.L.}=90\%\). Due to the fact that analysis is model-independent it allows for first measurement of the \(m(D_{s}K)\) spectrum, which is dominated by a pronounced peak around 2.6 GeV/\(c^{2}\).

Status and Results of the LHCb Experiment

Acta Phys. Pol. B 43, 1399 (2012)

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The LHCb experiment at the LHC has collected more than 1 fb\(^{-1}\) of physics data during the first two years of operation at the LHC, reaching one of its most important milestones. This has allowed the experiment to already perform extensive world-class measurements in \(b\) and \(c\)-physics, in order to probe New Physics Beyond the Standard Model. In this paper, the status and excellent performance of the LHCb experiment are reviewed, focusing the attention on the most important aspects of the operation of the experiment. Moreover, several important physics results are highlighted together with their impact for the full physics program at the LHC. Finally, a description of the upgrade of the detector to collect more than 50 fb\(^{-1}\) starting in 2018 will be also given.

Heavy Flavor Physics in LHCb

Acta Phys. Pol. B 43, 1413 (2012)

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This contribution summarises some of the main measurements performed by the LHCb experiment on heavy flavor physics, using data samples recorded during 2010 and 2011 in proton–proton collisions at \(\sqrt {s} = 7\) TeV.

BSM Models Facing the Recent LHCb Data: A First Look

Acta Phys. Pol. B 43, 1427 (2012)

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During the last decade a number of detailed analyses of flavour observables and of their correlations within more than a dozen specific BSM models have been performed at the TUM. One of the goals of these analyses was to investigate which model is capable of obtaining large mixing induced CP asymmetry in the \(B_s\) system, \(S_{\psi \phi }\), and to find out what this would imply for other flavour observables. In this context, also the rare decays \(B_{s,d}\to \mu ^+\mu ^-\) have been considered. In some models, their branching ratios can be enhanced by orders of magnitude above the SM expectations. The recent data on \(S_{\psi \phi }\) and \(B_{s,d}\to \mu ^+\mu ^-\) from the LHCb put an end to these very optimistic hopes modifying significantly the allowed patterns of deviations from SM predictions for flavour observables in concrete BSM models. We make a first semi-quantitative assessment of the most important modifications in the predictions of the BSM models in question including also recently analyzed models and taking into account the most recent lattice input. Our presentation is dominated by quark flavour observables in \(B_{s,d}\) and \(K^+(K^0)\) meson systems. For some BSM models the LHCb data turned out to be a relief. On the other hand, the SM models with CMFV and MFV models without flavour blind phases appear to have significant difficulties in describing all \(\Delta F=2\) observables in \(B_{s,d}\) and \(K^0\) meson systems simultaneously. However, definite conclusions will only be possible when \(|V_{ub}|\) and \(\gamma \) will be known from tree level decays with a much better precision and the lattice input will further improve. Finally, we propose to regard the stringent CMFV relations between various observables as standard candles of flavour physics. The pattern of deviations from these relations may help in identifying the correct NP scenario.

The Silicon Vertex Tracker for SuperB

Acta Phys. Pol. B 43, 1473 (2012)

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We present the latest development of the SuperB Silicon Vertex Tracker (SVT). After a short review on the physics requirements and technical challenges for the SuperB SVT, we discuss different candidate solutions for the inner most layer (layer0) of the SVT, namely strip and pixel detectors. Finally, we present the current preliminary test beam results for Striplets and Hybrid Pixels.

The Measurement of Branching Ratio of \(B_s^0 \rightarrow D^{\mp }_{s}K^{\pm }\) and \(B_s^0 \rightarrow D^{-}_{s}\pi ^{+}\) in the LHCb Experiment

Acta Phys. Pol. B 43, 1483 (2012)

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The document reports the first observation of the \(B_s^0 \rightarrow D^{\mp }_{s}K^{\pm }\) decays in the LHCb experiment together with the measurement of its branching fraction relative to the Cabibbo-favoured mode \(B_s^0 \rightarrow D^{-}_{s}\pi ^{+}\), \(\frac {B(B_s^0 \rightarrow D^{\mp }_{s}K^{\pm })}{B(B_s^0 \rightarrow D^{-}_{s}\pi ^{+})}\) \(= 0.0647\pm 0.0044({\rm stat.})^{+0.0039}_{-0.0043}({\rm syst.})\). Furthermore, combining the yields obtained from 2010 data and the semileptonic LHCb measurements of the ratio of \(b\)-fragmentation fractions \(f_s/f_d\), the branching fraction of the decay \(B_s^0 \rightarrow D^{-}_{s}\pi ^{+}\) is calculated, \(B(B_s^0 \rightarrow D^{-}_{s}\pi ^{+})=(3.04 \pm 0.19({\rm stat.})\pm 0.23({\rm syst.})^{+0.18}_{-0.16}(f_s/f_d))10^{-3}\). Finally, both measurements are used to obtain the absolute branching fraction of the \(B_s^0 \rightarrow D^{\mp }_{s}K^{\pm }\) decay, \(B(B_s^0 \rightarrow D^{\mp }_{s}K^{\pm })=(1.97\pm 0.18({\rm stat.})^{+0.19}_{-0.20}({\rm syst.})^{+0.11}_{-0.10}(f_s/f_d ))10^{-4}\). The branching fraction measurements are significantly more precise than the existing world average values. The analysis is based on a 370 pb\(^{-1}\) data sample collected in 2011 at LHC.

\(\phi _3\) Measurements at \(B\) Factories

Acta Phys. Pol. B 43, 1495 (2012)

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Precision of the determination of the CP-violating angle \(\phi _3\) has been improved by various measurements on the decays \(B^\pm \rightarrow D^{(*)}K^{(*)\pm }\). In this report, we show several recent updates which provide important ingredients in determining \(\phi _3\).

Pulse Shape Discrimination in Liquid Argon and Its Implications for Dark Matter Searches Using Depleted Argon

Acta Phys. Pol. B 43, 1509 (2012)

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A brief outline of Dark Matter detection experiments using liquid argon technology is presented. The Pulse Shape background discrimination method (PSD) is described and the example of its use in 2.3 l R&D detector is given. Methods of calculating sensitivity of a Dark Matter detector are discussed and used to estimate the possible improvement of sensitivity after introduction of isotopically depleted liquid argon.

Version corrected according to Erratum Acta Phys. Pol. B 43, 1911 (2012)

CP Violation Beyond Standard Model

Acta Phys. Pol. B 43, 1521 (2012)

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The study of CP violation in systems where it is expected to be suppressed and in systems where it is expected to be approximately the same as in the “golden” \(b \rightarrow c\bar {c}s\) transitions, provides an excellent laboratory for the search for physics beyond the Standard Model. Hadronic \(b \rightarrow s\bar {q} q\) decays, radiative \(b \rightarrow s\gamma \) events, charm and tau decays are selected from the samples of events collected by the BaBar and Belle detectors by means of several strategies. Standard Model tests are performed through measurements of \(B^0\rightarrow K^0_{\rm S} K^0_{\rm S} K^0_{\rm S}\) and \(B^0\rightarrow \phi K^0_{\rm S} \gamma \) time-dependent CP asymmetries, \(D^+_{(s)} \rightarrow K^+ K^0_{\rm S} \pi ^+ \pi ^-\) T-odd correlations, \(D^+ \rightarrow \phi \pi ^+\) time-integrated CP asymmetry and \(\tau ^-\rightarrow \pi ^- K^0_{\rm S} \nu _{\tau }\) decay-rate CP asymmetry. Limits on the charged Higgs boson couplings in the multi-Higgs-doublet scenario are obtained from the study of the relevant angular distributions in \(\tau ^-\rightarrow \pi ^- K^0_{\rm S}\nu _{\tau }\) decays.

CP Violation in the \(B\) System with the LHCb Experiment

Acta Phys. Pol. B 43, 1537 (2012)

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During 2011, LHCb has collected an integrated luminosity of 1.1 fb\(^{-1}\), giving rise to a large variety of measurements. Amongst these, measurements of CP violation in \(B\) decays play a central role. Three highlights are presented in this paper. The evidence for \(b \to u\) transitions in \(B^{\pm }\to DK^{\pm }\) is obtained, confirming recent BELLE results. The first evidence for direct CP violation in the \(B^0_s\) system is presented and CP violation is observed in the \(B^0\) system, using respectively \(B^0_s \to K^-\pi ^+\) and \(B^0\to K^+\pi ^-\) decays. An unambiguous world leading measurement of the mixing phase \(\phi _s\) of the \(B^0_s\) system is obtained by looking at \(b \to c \bar {c} s\) transitions.

Time-dependent CP Violation and Mixing at \(B\) Factories

Acta Phys. Pol. B 43, 1553 (2012)

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In the last decade, two \(B\)-factory experiments, BaBar and Belle performed a large number of measurements related to time-dependent CP violation and \(B\)–\(\overline {B}^0\) mixing. Achievements of those measurements are reviewed and possible room for New Physics is discussed.

The Measurement of the \(f_s/f_d\) Ratio from Hadronic Modes in the LHCb Experiment

Acta Phys. Pol. B 43, 1561 (2012)

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In this paper, the measurement of the fragmentation factor ratio \(f_s/f_d\) in the LHCb experiment using hadronic decay modes is presented. The relative yields of the three channels \(B^0 \to D^-\pi ^+\), \(B^0 \to D^-K^+\), \(B^0_s \to D^-_s\pi ^+\) selected from 35 pb\(^{-1}\) of data collected in 2010 are used for the analysis. The fragmentation fraction ratio is determined to be \(f_s/f_d = 0.245\pm 0.017^{\rm stat}\pm 0.018^{\rm syst}\pm 0.018^{\rm theor}\).

Hadronic and Rare \(B\) Decays with the BaBar and Belle Experiments

Acta Phys. Pol. B 43, 1573 (2012)

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We review recent experimental results on \(B_d\) and \(B_s\) mesons decays by the BaBar and Belle experiments. These include measurements of the color-suppressed decays \(\bar {B}^0\rightarrow D^{(*)0}h^0,h^0=\pi ^0,\eta ,\eta ^{\prime },\omega \), observation of the baryonic decay \(\bar {B}^0\rightarrow {\mit \Lambda }_c^+\bar {{\mit \Lambda }}K^-\), measurements of the charmless decays \(B\rightarrow \eta h,h=\pi ,K\), \(B\rightarrow K\pi \), and observation of CP eigenstates in the \(B_s\) decays: \(B^0_s\rightarrow J/\psi f_0(980)\), \(B^0_s\rightarrow J/\psi f_0(1370)\) and \(B^0_s\rightarrow J/\psi \eta \). The theoretical implications of these results will be considered.

Semileptonic \(B\) Decays and Implications for Higgs Searches

Acta Phys. Pol. B 43, 1581 (2012)

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We present recent results on semileptonic \(B\) decays from the BaBar experiment, with emphasis on \(\overline {B} \to D^{(*)}\tau \bar {\nu }\) and the implications that these decays have on our understanding of the Standard Model and New Physics effects.

Rare Decays at LHCb

Acta Phys. Pol. B 43, 1593 (2012)

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LHCb is one of the four major experiments at the Large Hadron Collider at CERN and is custom built to look for CP violation and New Physics in rare decays of the \(B\) and \(D\) mesons. Rare decays that occur via loop diagrams provide a way to probe New Physics at energy scales much higher than can be probed by direct production. In this article, the LHCb analyses of \(B \to \mu ^+\mu ^-\), \(B_d \to K^{*0}\mu ^+\mu ^-\) and \(B\to V\gamma \) and their results are reported.

full authors' list

T. Stavreva, F.I. Olness, I. Schienbein, T. Ježo, A. Kusina, K. Kovařík, J.Y. Yu

Heavy Quark Production in the ACOT Scheme Beyond NLO

Acta Phys. Pol. B 43, 1607 (2012)

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We compute the structure functions \(F_{2}\) and \(F_{\rm L}\) in the ACOT scheme for heavy quark production. We use the complete ACOT results to NLO, and make use of the \(\overline {\rm MS}\) massless results at NNLO and N\(^{3}\)LO to estimate the higher order mass-dependent corrections. We show numerically that the dominant heavy quark mass effects can be taken into account using massless Wilson coefficients together with an appropriate rescaling prescription. Combining the exact NLO ACOT scheme with these expressions should provide a good approximation to the full calculation in the ACOT scheme at NNLO and N\(^{3}\)LO.

New Mechanisms of Charm Production

Acta Phys. Pol. B 43, 1623 (2012)

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We discuss production of charm quarks, mesons as well as nonphotonic electrons in \(pp\) scattering at RHIC. The distributions in rapidity and transverse momentum of charm and bottom quarks/antiquarks are calculated in the \(k_{\rm t}\)-factorization approach. The hadronization of heavy quarks is done by means of phenomenological fragmentation functions and semileptonic decay functions are found by fitting semileptonic decay data. Good description of the inclusive data at large transverse momenta of electrons is obtained and a missing strength at small transverse momenta of electrons is found. In addition, we discuss kinematical correlations between charged leptons from different mechanisms. Reactions initiated by purely QED \(\gamma ^*\gamma ^*\)-fusion in elastic and inelastic \(pp\) collisions as well as diffractive mechanism of exclusive \(c \bar c\) production are included. A good description of the dilepton invariant mass spectrum of the PHENIX Collaboration is achieved. Distributions in the dilepton pair transverse momentum and in azimuthal angle between electron and positron are presented. A new mechanism of exclusive production of \(c \bar c\) is discussed. Corresponding results are shown and the possibility of its identification is discussed. We discuss also production of two pairs of \(c \bar c\) within a simple formalism of double-parton scattering (DPS). Very large cross sections, comparable to single-\(c \bar c\) production, are predicted for LHC energies. Both total inclusive cross section as a function of energy and differential distributions are shown. We discuss a perspective how to identify the double scattering contribution.

Charm Physics in the LHCb Experiment, First Evidence for CP Violation in Charm Decays

Acta Phys. Pol. B 43, 1643 (2012)

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A search for the time integrated CP violation in the \(D^0\rightarrow h^-h^+\) (\(h=K,\pi \)) decays is presented using \(0.62~{\rm fb^{-1}}\) of data collected by the LHCb experiment in 2011. The flavour of the charm meson is determined by the charge of the slow pion in the \(D^{*+}\rightarrow D^0\pi ^+\) and the \(D^{*-}\rightarrow \bar {D}^0\pi ^-\) decays chain. The difference in CP asymmetry between the \(D^0\rightarrow K^-K^+\) and the \(D^0\rightarrow \pi ^-\pi ^+\), \(\Delta A_{\rm CP}\equiv A_{\rm CP}(K^-K^+)-A_{\rm CP}(\pi ^-\pi ^+)\), is measured to be \([-0.82\pm 0.21{\rm (stat)}\pm 0.11{\rm (syst)}]\%\). This differs from the hypothesis of CP conservation by \(3.5\) standard deviations. An additional search for the time integrated CP violation in the Cabibbo suppressed decay \(D^+\rightarrow K^-K^+\pi ^+\) is also presented. Here no evidence for CP asymmetry is found using a model independent method. The data used here was collected by the LHCb experiment in 2010 and corresponds to an integrated luminosity of \(35~{\rm pb^{-1}}\). The normalized Dalitz plot distributions for the \(D^+\) and the \(D^-\) are compared using two different binning schemes that are sensitive to different manifestations of CP violation.

The IFR Detector at SuperB

Acta Phys. Pol. B 43, 1653 (2012)

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The SuperB project is an international enterprise aiming at the construction of the high-luminosity asymmetric beam energy electron–positron accelerator, along with the dedicated detection system. The Instrumented Flux Return (IFR) is the subdetector designed primarily for the purposes of the muon identification. In this paper, the main physical goals are discussed and the overview of the baseline design for the IFR detector is given. Also, the IFR prototype and the studies on the test-beam data are presented.


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