Updated Next-to-Next-to-Leading-Order QCD Predictions for the Weak Radiative B -Meson Decays

Weak radiative decays of the B mesons belong to the most important flavor changing processes that provide constraints on physics at the TeV scale. In the derivation of such constraints, accurate standard model predictions for the inclusive branching ratios play a crucial role. In the current Letter we present an update of these predictions, incorporating all our results for the O(α2s) and lower-order perturbative corrections that have been calculated after 2006. New estimates of nonperturbative effects are taken into account, too. For the CP- and isospin-averaged branching ratios, we find Bsγ=(3.36±0.23)×10−4 and Bdγ=(1.73+0.12−0.22)×10−5, for Eγ>1.6  GeV. Both results remain in agreement with the current experimental averages. Normalizing their sum to the inclusive semileptonic branching ratio, we obtain Rγ≡(Bsγ+Bdγ)/Bcℓν=(3.31±0.22)×10−3. A new bound from Bsγ on the charged Higgs boson mass in the two-Higgs-doublet-model II reads MH±>480  GeV at 95% C.L.

A measurement of B0-B0 mixing in e+e- annihilation at 29 GeV

This thesis describes a measurement of B⁰- B⁰ mixing in events produced by electron-positron annihilation at a center of mass energy of 29 GeV. The data were taken by the Mark II detector in the PEP storage ring at the Stanford Linear Accelerator Center between 1981 and 1987, and correspond to a total integrated luminosity of 224pb^-1.

We used a new method, based on the kinematics of hadronic events containing two leptons, to provide a measurement of the probability, x, that a hadron, initially containing a b (b) quark decays to a positive (negative) lepton to be X = 0.17^+0.15b>-0.08b>, with 90% confidence level upper and lower limits of 0.38 and 0.06, respectively, including all estimated systematic errors. Because of the good separation of signal and background, this result is relatively insensitive to various systematic effects which have complicated previous measurements.

We interpret this result as evidence for the mixing of neutral B mesons. Based on existing B⁰b>db> mixing rate measurements, and some assumptions about the fractions of B⁰b>db> and B⁰b>sb> mesons present in the data, this result favors maximal mixing of B⁰b>sb> mesons, although it cannot rule out zero B⁰b>sb> mixing at the 90% confidence level.

Heavy-flavor measurements by the PHENIX experiment at RHIC

In recent years, PHENIX has studied many important observables related to heavy-flavor physics through their leptonic decay measurements including the invariant yield of electrons from nonphotonic sources, and prompt single muons, both of which are dominated by D and B mesons. Charm and beauty cross-sections were measured and compared through single lepton, and lepton-hadron correlations in p+p collisions at root s = 200 GeV. Observables for quarkonia production such as invariant yield and polarization were also measured in p+p collisions. In Au+Au collisions, preliminary results for the R(AA) for single electrons and a 90% CL upper limit for the suppression of s were produced. And in d+Au collisions, a preliminary R(CP) study for J/psi production in different centrality ranges was extracted.

CMS physics technical design report, volume II: Physics performance

CMS is a general purpose experiment, designed to study the physics of pp collisions at 14 TeV at the Large Hadron Collider ( LHC). It currently involves more than 2000 physicists from more than 150 institutes and 37 countries. The LHC will provide extraordinary opportunities for particle physics based on its unprecedented collision energy and luminosity when it begins operation in 2007. The principal aim of this report is to present the strategy of CMS to explore the rich physics programme offered by the LHC. This volume demonstrates the physics capability of the CMS experiment. The prime goals of CMS are to explore physics at the TeV scale and to study the mechanism of electroweak symmetry breaking - through the discovery of the Higgs particle or otherwise. To carry out this task, CMS must be prepared to search for new particles, such as the Higgs boson or supersymmetric partners of the Standard Model particles, from the start- up of the LHC since new physics at the TeV scale may manifest itself with modest data samples of the order of a few fb(-1) or less. The analysis tools that have been developed are applied to study in great detail and with all the methodology of performing an analysis on CMS data specific benchmark processes upon which to gauge the performance of CMS. These processes cover several Higgs boson decay channels, the production and decay of new particles such as Z' and supersymmetric particles, B-s production and processes in heavy ion collisions. The simulation of these benchmark processes includes subtle effects such as possible detector miscalibration and misalignment. Besides these benchmark processes, the physics reach of CMS is studied for a large number of signatures arising in the Standard Model and also in theories beyond the Standard Model for integrated luminosities ranging from 1 fb(-1) to 30 fb(-1). The Standard Model processes include QCD, B-physics, diffraction, detailed studies of the top quark properties, and electroweak physics topics such as the W and Z(0) boson properties. The production and decay of the Higgs particle is studied for many observable decays, and the precision with which the Higgs boson properties can be derived is determined. About ten different supersymmetry benchmark points are analysed using full simulation. The CMS discovery reach is evaluated in the SUSY parameter space covering a large variety of decay signatures. Furthermore, the discovery reach for a plethora of alternative models for new physics is explored, notably extra dimensions, new vector boson high mass states, little Higgs models, technicolour and others. Methods to discriminate between models have been investigated. This report is organized as follows. Chapter 1, the Introduction, describes the context of this document. Chapters 2-6 describe examples of full analyses, with photons, electrons, muons, jets, missing E-T, B-mesons and tau's, and for quarkonia in heavy ion collisions. Chapters 7-15 describe the physics reach for Standard Model processes, Higgs discovery and searches for new physics beyond the Standard Model.

Evidence for an anomalous like-sign dimuon charge asymmetry

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evidence for an Anomalous Like-Sign Dimuon Charge Asymmetry

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

QCD-Strahlungskorrekturen zu Polarisationsobservablen in semileptonischen Zerfällen schwerer Quarks

In dieser Arbeit werden die QCD-Strahlungskorrekturen in erster Ordnung der starken Kopplungskonstanten für verschiedene Polarisationsobservablen zu semileptonischen Zerfällen eines bottom-Quarks in ein charm-Quark und ein Leptonpaar berechnet. Im ersten Teil wird der Zerfall eines unpolarisierten b-Quarks in ein polarisiertes c-Quark sowie ein geladenes Lepton und ein Antineutrino im Ruhesystem des b-Quarks analysiert. Es werden die Strahlungskorrekturen für den unpolarisierten und den polarisierten Beitrag zur differentiellen Zerfallsrate nach der Energie des c-Quarks berechnet, wobei das geladene Lepton als leicht angesehen und seine Masse daher vernachlässigt wird. Die inklusive differentielle Rate wird durch zwei Strukturfunktionen in analytischer Form dargestellt. Anschließend werden die Strukturfunktionen und die Polarisation des c-Quarks numerisch ausgewertet. Nach der Einführung der Helizitäts-Projektoren befaßt sich der zweite Teil mit dem kaskadenartigen Zerfall eines polarisierten b-Quarks in ein unpolarisiertes c-Quark und ein virtuelles W-Boson, welches weiter in ein Paar leichter Leptonen zerfällt. Es werden die inklusiven Strahlungskorrekturen zu drei unpolarisierten und fünf polarisierten Helizitäts-Strukturfunktionen in analytischer Form berechnet, welche die Winkelverteilung für die differentielle Zerfallsrate nach dem Viererimpulsquadrat des W-Bosons beschreiben. Die Strukturfunktionen enthalten die Informationen sowohl über die polare Winkelverteilung zwischen dem Spinvektor des b-Quarks und dem Impulsvektor des W-Bosons als auch über die räumliche Winkelverteilung zwischen den Impulsen des W-Bosons und des Leptonpaars. Der Impuls und der Spinvektor des b-Quarks sowie der Impuls des W-Bosons werden im b-Ruhesystem analysiert, während die Impulse des Leptonpaars im W-Ruhesystem ausgewertet werden. Zusätzlich zu den genannten Strukturfunktionen werden noch die unpolarisierte und die polarisierte skalare Strukturfunktion angegeben, die in Anwendungen bei hadronischen Zerfällen eine Rolle spielen. Anschließend folgt eine numerische Auswertung aller berechneten Strukturfunktionen. Im dritten Teil werden die nichtperturbativen HQET-Korrekturen zu inklusiven semileptonischen Zerfällen schwerer Hadronen diskutiert, welche ein b-Quark enthalten. Sie beschreiben hadronische Korrekturen, die durch die feste Bindung des b-Quarks in Hadronen hervorgerufen werden. Es werden insgesamt fünf unpolarisierte und neun polarisierte Helizitäts-Strukturfunktionen in analytischer Form angegeben, die auch eine endliche Masse und den Spin des geladenen Leptons berücksichtigen. Die Strukturfunktionen werden sowohl in differentieller Form in Abhängigkeit des quadrierten Viererimpulses des W-Bosons als auch in integrierter Form präsentiert. Zum Schluß werden die zuvor erhaltenen Resultate auf die semi-inklusiven hadronischen Zerfälle eines polarisierten Lambda_b-Baryons oder eines B-Mesons in ein D_s- oder ein D_s^*-Meson unter Berücksichtigung der D_s^*-Polarisation angewandt. Für die zugehörigen Winkelverteilungen werden die inklusiven QCD- und die nichtperturbativen HQET-Korrekturen zu den Helizitäts-Strukturfunktionen in analytischer Form angegeben und anschließend numerisch ausgewertet.

Relative rates of B meson decays into psi(2S) and J/psi mesons

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Heavy-light mesons on a lattice

Several excited states of Ds and Bs mesons have been discovered in the last six years: BaBar, Cleo and Belle discovered the very narrow states D(s0)*(2317)+- and D(s1)(2460)+- in 2003, and CDF and DO Collaborations reported the observation of two narrow Bs resonances, B(s1)(5830)0 and B*(s2)(5840)0 in 2007. To keep up with experiment, meson excited states should be studied from the theoretical aspect as well. The theory that describes the interaction between quarks and gluons is quantum chromodynamics (QCD). In this thesis the properties of the meson states are studied using the discretized version of the theory - lattice QCD. This allows us to perform QCD calculations from first principles, and "measure" not just energies but also the radial distributions of the states on the lattice. This gives valuable theoretical information on the excited states, as we can extract the energy spectrum of a static-light meson up to D wave states (states with orbital angular momentum L=2). We are thus able to predict where some of the excited meson states should lie. We also pay special attention to the order of the states, to detect possible inverted spin multiplets in the meson spectrum, as predicted by H. Schnitzer in 1978. This inversion is connected to the confining potential of the strong interaction. The lattice simulations can also help us understand the strong interaction better, as the lattice data can be treated as "experimental" data and used in testing potential models. In this thesis an attempt is made to explain the energies and radial distributions in terms of a potential model based on a one-body Dirac equation. The aim is to get more information about the nature of the confining potential, as well as to test how well the one-gluon exchange potential explains the short range part of the interaction.

Production of psi(2S) Mesons in ppbar Collisions at 1.96 TeV

We have measured the differential cross section for the inclusive production of psi(2S) mesons decaying to mu^{+} mu^{-1} that were produced in prompt or B-decay processes from ppbar collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of 1.1 fb^{-1} collected by the CDF II detector at Fermilab. For events with transverse momentum p_{T} (psi(2S)) > 2 GeV/c and rapidity |y(psi(2S))| psi(2S)X) Br(psi(2S) -> mu^{+} mu^{-}) to be 3.29 +- 0.04(stat.) +- 0.32(syst.) nb.

First Measurement of the Ratio of Branching Fractions B(Lambda_b to Lambda_c mu nu)/B(Lambda_b to Lambda_c pi)

The analysis uses data from an integrated luminosity of approximately 172 pb-1 of ppbar collisions at sqrt(s)=1.96 TeV, collected with the CDF II detector at the Fermilab Tevatron. The Lambda_b and B0 relative branching fractions are measured to be: B(Lambda_b to Lambda_c+ mu nu)/B(Lambda_b to Lambda_c+ pi) = 16.6 +- 3.0 (stat) +- 1.0 (syst) +2.6 -3.4 (PDG) +- 0.3 (EBR), B(B0 to D+ mu nu)/B(B0 to D+ pi) = 9.9 +- 1.0 (stat) +- 0.6 (syst) +- 0.4 (PDG) +- 0.5 (EBR), B(B0 to D*+ mu nu)/B(B0 to D*+ pi) = 16.5 +- 2.3 (stat) +- 0.6 (syst) +- 0.5 (PDG) +- 0.8 (EBR) This article also presents measurements of the branching fractions of four new Lambda_b semileptonic decays: Lambda_b to Lambda_c(2595)+ mu nu, Lambda_b to Lambda_c(2625)+ mu nu, Lambda_b to Sigma_c(2455)0 pi mu nu, Lambda_b to Sigma_c(2455)++ pi mu nu, relative to the branching fraction of the Lambda_b to Lambda_c mu nu decay. Finally, the transverse-momentum distribution of Lambda_b baryons produced in p-pbar collisions is measured and found to be significantly different from that of B0 mesons.

First measurement of the ratio of branching fractions B(Λb0→Λc+μ-ν̅ μ)/B(Λb0→Λc+π-)

This article presents the first measurement of the ratio of branching fractions B(Λb0→Λc+μ-ν̅ μ)/B(Λb0→Λc+π-). Measurements in two control samples using the same technique B(B̅ 0→D+μ-ν̅ μ)/B(B̅ 0→D+π-) and B(B̅ 0→D*(2010)+μ-ν̅ μ)/B(B̅ 0→D*(2010)+π-) are also reported. The analysis uses data from an integrated luminosity of approximately 172  pb-1 of pp̅ collisions at √s=1.96  TeV, collected with the CDF II detector at the Fermilab Tevatron. The relative branching fractions are measured to be B(Λb0→Λc+μ-ν̅ μ)/B(Λb0→Λc+π-)=16.6±3.0(stat)±1.0(syst)+2.6/-3.4(PDG)±0.3(EBR), B(B̅ 0→D+μ-ν̅ μ)/B(B̅ 0→D+π-)= 9.9±1.0(stat)±0.6(syst)±0.4(PDG)±0.5(EBR), and B(B̅ 0→D*(2010)+μ-ν̅ μ)/B(B̅ 0→D*(2010)+π-)=16.5±2.3(stat)± 0.6(syst)±0.5(PDG)±0.8(EBR). The uncertainties are from statistics (stat), internal systematics (syst), world averages of measurements published by the Particle Data Group or subsidiary measurements in this analysis (PDG), and unmeasured branching fractions estimated from theory (EBR), respectively. This article also presents measurements of the branching fractions of four new Λb0 semileptonic decays: Λb0→Λc(2595)+μ-ν̅ μ, Λb0→Λc(2625)+μ-ν̅ μ, Λb0→Σc(2455)0π+μ-ν̅ μ, and Λb0→Σc(2455)++π-μ-ν̅ μ, relative to the branching fraction of the Λb0→Λc+μ-ν̅ μ decay. Finally, the transverse-momentum distribution of Λb0 baryons produced in pp̅ collisions is measured and found to be significantly different from that of B̅ 0 mesons, which results in a modification in the production cross-section ratio σΛb0/σB̅ 0 with respect to the CDF I measurement.