M. Margoni

This paper reports world averages of measurements of b-hadron, c-hadron, and τ-lepton properties obtained by the Heavy Flavor Averaging Group using results available before April 2021. In rare cases, significant results obtained several months later are also used. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, parameters of semileptonic decays, and Cabibbo-Kobayashi-Maskawa matrix elements.97 MoreReceived 25 June 2022Accepted 20 September 2022DOI:https://doi.org/10.1103/PhysRevD.107.052008Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBound statesCabibbo–Kobayashi–Maskawa matrixChiral perturbation theoryElectroweak interactionFlavor changing neutral currentsForm factorsHadron mixingLattice QCDParticle decaysParticle interactionsParticle mixing & oscillationsQuark mixingParticles & Fields

DELPHI data collected at centre-of-mass energies up to 208 GeV have been analysed to search for charginos, neutralinos and sfermions in the framework of the Minimal Supersymmetric Standard Model (MSSM) with R-parity conservation. No evidence for a signal was found in any of the channels. The results of each search were used to derive limits on production cross-sections and particle masses. In addition, the combined result of all searches excludes regions in the parameter space of the constrained MSSM, leading to limits on the mass of the Lightest Supersymmetric Particle and other supersymmetric particles.

The physics objectives of SuperB, an asymmetric electron-positron collider with a luminosity above 10^36/cm^2/s are described, together with the conceptual design of a novel low emittance design that achieves this performance with wallplug power comparable to that of the current B Factories, and an upgraded detector capable of doing the physics in the SuperB environment.

The Compact Muon Solenoid (CMS) experiment prepares its Phase-2 upgrade for the high-luminosity era of the LHC operation (HL-LHC). Due to the increase of occupancy, trigger latency and rates, the full electronics of the CMS Drift Tube (DT) chambers will need to be replaced. In the new design, the time bin for the digitization of the chamber signals will be of around 1 ns, and the totality of the signals will be forwarded asynchronously to the service cavern at full resolution. The new backend system will be in charge of building the trigger primitives of each chamber. These trigger primitives contain the information at chamber level about the muon candidates position, direction, and collision time, and are used as input in the L1 CMS trigger. The added functionalities will improve the robustness of the system against ageing. An algorithm based on analytical solutions for reconstructing the DT trigger primitives, called Analytical Method, has been implemented both as a software C++ emulator and in firmware. Its performance has been estimated using the software emulator with simulated and real data samples, and through hardware implementation tests. Measured efficiencies are 96 to 98% for all qualities and time and spatial resolutions are close to the ultimate performance of the DT chambers. A prototype chain of the HL-LHC electronics using the Analytical Method for trigger primitive generation has been installed during Long Shutdown 2 of the LHC and operated in CMS cosmic data taking campaigns in 2020 and 2021. Results from this validation step, the so-called Slice Test, are presented.

We present a study of ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{K}_{S}^{0}{K}_{S}^{0}({\ensuremath{\pi}}^{0}){\ensuremath{\nu}}_{\ensuremath{\tau}}$ and ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}_{S}^{0}{K}_{S}^{0}({\ensuremath{\pi}}^{0}){\ensuremath{\nu}}_{\ensuremath{\tau}}$ decays using a data set of 430 million $\ensuremath{\tau}$ lepton pairs, corresponding to an integrated luminosity of $468\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, collected with the BABAR detector at the PEP-II asymmetric energy ${e}^{+}{e}^{\ensuremath{-}}$ storage rings. We measure branching fractions of $(2.31\ifmmode\pm\else\textpm\fi{}0.04\ifmmode\pm\else\textpm\fi{}0.08)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $(1.60\ifmmode\pm\else\textpm\fi{}0.20\ifmmode\pm\else\textpm\fi{}0.22)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ for the ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{K}_{S}^{0}{K}_{S}^{0}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ and ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{K}_{S}^{0}{K}_{S}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ decays, respectively. We find no evidence for ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}_{S}^{0}{K}_{S}^{0}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ and ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}_{S}^{0}{K}_{S}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ decays and place upper limits on the branching fractions of $6.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ and $4.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ at the 90% confidence level.

The CMS drift tubes (DT) muon detector, built for withstanding the LHC expected integrated and instantaneous luminosities, will be used also in the High Luminosity LHC (HL-LHC) at a 5 times larger instantaneous luminosity and, consequently, much higher levels of radiation, reaching about 10 times the LHC integrated luminosity. Initial irradiation tests of a spare DT chamber at the CERN gamma irradiation facility (GIF++), at large (∼ O(100)) acceleration factor, showed ageing effects resulting in a degradation of the DT cell performance. However, full CMS simulations have shown almost no impact in the muon reconstruction efficiency over the full barrel acceptance and for the full integrated luminosity. A second spare DT chamber was moved inside the GIF++ bunker in October 2017. The chamber was being irradiated at lower acceleration factors, and only 2 out of the 12 layers of the chamber were switched at working voltage when the radioactive source was active, being the other layers in standby. In this way the other non-aged layers are used as reference and as a precise and unbiased telescope of muon tracks for the efficiency computation of the aged layers of the chamber, when set at working voltage for measurements. An integrated dose equivalent to two times the expected integrated luminosity of the HL-LHC run has been absorbed by this second spare DT chamber and the final impact on the muon reconstruction efficiency is under study. Direct inspection of some extracted aged anode wires presented a melted resistive deposition of materials. Investigation on the outgassing of cell materials and of the gas components used at the GIF++ are underway. Strategies to mitigate the ageing effects are also being developed. From the long irradiation measurements of the second spare DT chamber, the effects of radiation in the performance of the DTs expected during the HL-LHC run will be presented.

A novel technique for longitudinal segmentation of shashlik calorimeters has been tested in the CERN West Area beam facility. A 25 tower very fine samplings e.m. calorimeter has been built with vacuum photodiodes inserted in the first 8 radiation lengths to sample the initial development of the shower. Results concerning energy resolution, impact point reconstruction and electron/pion separation are reported.

Two techniques for longitudinal segmentation of shashlik calorimeters are proposed. Results concerning energy resolution and e/π separation are reported.

We present a new measurement of CP violation induced by B0 B0bar oscillations, based on the full data set collected by the BaBar experiment at the PEPII collider. We use a sample of about 6 million B0->D* l nu decays selected with partial reconstruction of the D* meson. The charged lepton identifies the flavor of the first B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine the parameter dCP = 1 - |q/p| = (0.29+-0.84+1.78/-1.61) 10^-3.

We report a Dalitz plot analysis of charmless hadronic decays of charged $B$ mesons to the final state $K_{\rm S}^{0}\pi^{+}\pi^{0}$ using the full BaBar dataset of $470.9\pm2.8$ million $B\bar{B}$ events collected at the $\Upsilon(4S)$ resonance. We measure the overall branching fraction and $CP$ asymmetry to be ${\cal B}\left(B^{+}\to K^{0}\pi^{+}\pi^{0}\right) = \left(45.9 \pm 2.6 \pm 3.0^{+8.6}_{-0.0}\right)\times10^{-6}$ and $A_{CP}\left(B^{+}\to K^{0}\pi^{+}\pi^{0}\right) = 0.07 \pm 0.05 \pm 0.03^{+0.02}_{-0.03}$, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for $B^{+} \to K^{0}\pi^{+}\pi^{0}$. We find first evidence of a $CP$ asymmetry in $B^{+}\to K^{*}(892)^{+}\pi^{0}$ decays: $A_{CP}\left(B^{+}\to K^{*}(892)^{+}\pi^{0}\right)=-0.52 \pm 0.14 \pm 0.04^{+0.04}_{-0.02}$. The significance of this asymmetry, including systematic and model uncertainties, is $3.4$ standard deviations. We also measure the branching fractions and $CP$ asymmetries for three other intermediate decay modes.

During the High Luminosity LHC, the Drift Tube chambers installed in the CMS detector need to operate with an integrated dose ten times higher than expected at the LHC due to the increase in integrated luminosity from 300 fb-1 to 3000 fb-1. Irradiations have been performed to assess the performance of the detector under such conditions and to characterize the radiation aging of the detector. The presented analysis focuses on the behaviour of the high voltage currents and the dose measurements needed to extrapolate the results to High Luminosity conditions, using data from the photon irradiation campaign at GIF++ in 2016 as well as the efficiency analysis from the irradiation campaign started in 2017. Although the single-wire loss of high voltage gain observed of 70% is very high, the muon reconstruction efficiency is expected to decrease less than 20% during the full duration of High Luminosity LHC in the areas under highest irradiation.

An update of a study of the production of single and multi-photon events with missing energy has been made with the data collected at p s = 202 209 GeV with the DELPHI detector. The analysis uses a total integrated luminosity of 654 pb 1 . No excess of events beyond that expected from the Standard Model was observed and limits are set on new physics as described by supersymmetric models. A new limit on the gravitational scale is also determined.

Flavor Changing Neutral Current transitions b→sγ and b→sl+l− provide an excellent laboratory for the search for physics beyond the Standard Model. Standard Model tests are performed through measurements of the B→Xsl+l− branching ratio, the B→Xsl+l− and B→Xsγ direct CP asymmetries, and the B0→Ks0π−π+γ time-dependent CP asymmetry. Strong constraints on the (tan⁡β,mH+) plane in the two-Higgs doublet models scenario are obtained from the measurements of the B+→τ+ν branching ratio and of the branching fractions ratio R(D(⁎))=B(B¯→D(⁎)τ−ντ¯)/B(B¯→D(⁎)l−νl¯), where l refers to either an electron or a muon.

In the frame of research and development for electromagnetic calorimetry at future e/sup +/e/sup -/ linear colliders, different techniques have been studied to implement longitudinal segmentation in Shashlik calorimeters. Two prototypes with 5/spl times/5 cm/sup 2/ lead/scintillator towers and readout by means of wavelength-shifting fibers have been built. The longitudinal segmentation of the shower is achieved by modifying the front part of the detector. In the first prototype, vacuum photodiodes have been inserted laterally for the first eight X/sub 0/, while in the second prototype a slow scintillator has been used in the first five X/sub 0/. Both of the prototypes have been exposed to beam at CERN. The performance in term of energy resolution, spatial resolution, and e//spl pi/ separation are described.

Standard Model predictions of the CP violation in the mixing of B0d and B0s mesons are beyond the present experimental sensitivity, any observation would be therefore a hint of new physics. The D0 collaboration measures a value of the semileptonic mixing asymmetry for a mixture of B0d and B0s mesons, AbSL, which misses the Standard Model expectation by 3.9 standard deviations. The world averages of the flavor specific measurements of the semileptonic asymmetries for B0d and B0s mesons, AdSL and AsSL, are instead in agreement with the Standard Model. The combination of the various AqSL (q=d, s) measurements and the recent LHCb results on B0s -> J/psi phi have placed tight bounds on the hypothesis of new physics which can explain the D0 result.

Flavour Changing Neutral Current transitions B → X s/d γ and B → X s/d l + l -provide an excellent laboratory for the search for physics beyond the Standard Model and for the study of the dynamics of b-quark inside B mesons.B → X s/d γ and B → X s/d l + l -decays are selected from the samples of events collected by the BaBar, Belle and CDF detectors by means of several strategies.Standard Model tests are performed through measurements of inclusive BR(B → X s/d γ), BR(B → X s/d l + l -), CP and isospin asymmetries, and the study of the relevant angular distributions in B → X s/d l + l -decays.A |V td /V ts | measurement with reduced theoretical uncertainties is obtained from the branching fraction ratio BR(b → dγ)/BR(b → sγ).The most precise |V cb | determination is extracted by global fits to the moments of inclusive distributions in B → X c lν and B → X s γ using the kinetic mass scheme.Uncertainties on shape functions in the measurement of |V ub | using inclusive semileptonic decays B → X u lν are limited by comparing the partial rates for B → X u lν and B → X s γ in restricted phase space regions.

We present a new measurement of CP violation induced by B0 B0bar oscillations, based on the full data set collected by the BaBar experiment at the PEPII collider. We use a sample of about 6 million B0->D* l nu decays selected with partial reconstruction of the D* meson. The charged lepton identifies the flavor of the first B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine the parameter dCP = 1 - |q/p| = (0.29+-0.84+1.78/-1.61) 10^-3.

Flavor Changing Neutral Current transitions b→sl+l− and b→sγ provide an excellent laboratory for the search for physics beyond the Standard Model. Standard Model tests are performed through measurements of the lepton forward-backward asymmetry AFB and the longitudinal K* polarization FL in the decay B→K⁎l+l−, and the search for the rare decay B+→K+τ+τ−. From the study of the Kπ+π− system in B radiative-penguin decays, the time-dependent CP asymmetry in the decay B0→KS0π+π−γ is measured, together with the branching fractions of B+→K+π−π+γ and B0→K0π−π+γ.

Differential production cross sections of the B+ meson and of J/ψ, ψ(2S), and ϒ(nS) (n=1,2,3) vector mesons are measured in pp collisions at 13 TeV, as a function of transverse momentum and rapidity, using data collected by the CMS detector in 2015. The B+ is reconstructed in the decay channel B+→J/ψK+ and the five S-wave quarkonium states are reconstructed in the dimuon decay channel. The simultaneous production of two ϒ(1S) mesons in observed at s=8 TeV in a data sample corresponding to an integrated luminosity of L=20.7 fb−1. The angular distributions and the differential branching fraction of the flavor changing neutral current decay B0→K⁎0μ+μ− are studied using data collected at s=8 TeV, as a function of the dimuon invariant mass squared. Flavor changing neutral currents in top quark couplings are searched through single top quark production in association with a photon, and in tt‾→Zq+Wb and tt‾→Hq+Wb decays, where Z→l+l− and H→γγ, WW, ZZ, τ+τ− and bb‾. The observed number of events agrees with the Standard Model prediction, and no evidence of flavor changing neutral currents is found.

To sustain and extend its discovery potential, the Large Hadron Collider (LHC) will undergo a major upgrade in the coming years, referred to as High Luminosity LHC (HLLHC), aimed to increase its instantaneous luminosity, 5 times larger than the designed limit, and, consequently leading to high levels of radiation, with the goal to collect 10 times larger the original designed integrated luminosity. The drift tube chambers (DT) of CMS muon detector system is built to proficiently measure and trigger on muons in the harsh radiation environment expected during the HL-LHC era. Ageing studies are performed at the CERNs gamma ray irradiation facility (GIF++) by measuring the muon hit efficiency of these detectors at various LHC operation conditions. One such irradiation campaign was started in October 2017, when a spare MB2 chamber moved inside the bunker and irradiated at lower acceleration factors. Two out of twelve layers of the DT chamber were operated while being irradiated with the radioactive source and then their muon hit efficiency was calculated in coincidence with other ten layers which were kept on the standby. The chamber absorbed an integrated dose equivalent to two times the expected integrated luminosity of the HL-LHC. Investigation on the outgassing of cell materials and of the gas components used at the GIF++ are underway and strategies to mitigate the aging effects are also being developed. The effect of radiation on the performance of DT chamber and its impact on the overall muon reconstruction efficiency expected during the HL-LHC are presented.

We have constructed a prototype of an electromagnetic calorimeter, for future linear collider experiments, alternating 45 layers of lead and scintillator planes. The scintillation light is collected by means of WLS fibers from square cells of 5/spl times/5 cm/sup 2/. To improve the reconstruction of the shower profile, three silicon pad (/spl sim/0.9/spl times/0.9 cm/sup 2/) detector planes have been inserted between the lead and scintillator layers at 2.6 and 12 X/sub 0/. The prototype has been tested with electron beams at low (50/spl divide/750 MeV) and high energies (5/spl divide/50 GeV): a good linearity in response and an energy resolution of /spl sim/11.5%//spl radic/(E/GeV) have been achieved. A position resolution of 2.5 mm has also been measured for 10 GeV impinging electrons. The calorimeter particle identification capability has been tested comparing electron and pion beams.

A prototype of an electromagnetic sampling calorimeter for future linear collider experiments has been commissioned by the LCCAL collaboration. In order to improve the reconstruction of the shower profile, three silicon pad detector planes have been inserted between lead and scintillator layers at 2, 6 and 12 X/sub 0/. The scintillator light is collected by means of lateral W.L.S. fibers. The electrical parameters of the pad detectors have been determined by a static IV and CV characterisation; charge collection efficiency and tracking capability have been measured during beam tests. Results from test-beam runs are shown.

The inclusive direct b → l− and cascade b → c → l+ semileptonic branching ratios of the b quark were measured by the four LEP collaborations by means of several strategies. The first inclusive measurement of BR(b → c̄ → l−) was obtained by DELPHI. From the BR(b → l−) LEP average, the most precise determination of the |Vcb| coupling constant was then extracted in the OPE approach.

Two techniques for longitudinal segmentation of shashlik calorimeters are proposed. Results concerning energy resolution, impact point reconstruction and e//spl pi/ separation are reported.

Two techniques for longitudinal segmentation of shashlik calorimeters are proposed. Results concerning energy resolution, impact point reconstruction and e/n separation are reported.

Combined results on b-hadron lifetimes, b-hadron production rates, B{sub d}{sup 0}-{bar B}{sub d}{sup 0} and B{sub s}{sup 0}-{bar B}{sub s}{sup 0} oscillations, the decay width difference between the mass eigenstates of the B{sub s}{sup 0}-{bar B}{sub s}{sup 0} system, the average number of c and {bar c} quarks in b-hadron decays, and searches for CP violation in the B{sub d}{sup 0}-{bar B}{sub d}{sup 0} system are presented. They have been obtained from published and preliminary measurements available in Summer 2000 from the ALEPH, CDF, DELPHI, L3, OPAL and SLD Collaborations. These results have been used to determine the parameters of the CKM unitarity triangle.

Conveners: E. Barberio, L. Lellouch, K.R. Schubert Contributors: M. Artuso, M. Battaglia, C. Bauer, D. Becirevic, M. Beneke, I. Bigi, T. Brandt, D. Cassel, M. Calvi, M. Ciuchini, A. Dighe ,K. Ecklund, P. Gagnon, P. Gambino, S. Hashimoto, A. Hoang, T. Hurth, A. Khodjamirian, C.S. Kim, A. Kronfeld, A. Lenz, A. Le Yaouanc, Z. Ligeti, V. Lubicz, D. Lucchesi, T. Mannel, M. Margoni, G. Martinelli, D. Melikhov, V. Morenas, H.G. Moser, L. Oliver, O. Pene, J.C. Raynal, P. Roudeau, C. Schwanda, B. Serfass, M. Smizanska, J. Stark, B. Stech, A. Stocchi, N. Uraltsev, A. Warburton, L.H. Wilden.

The production of single and multi-photon events has been studied in the reaction e + e ! ( ) + invisible particles. The data collected with the DELPHI detector during the years 1999 and 2000 at centre-of-mass energies between 192 GeV and 209 GeV was combined with earlier data to search for phenomena beyond the Standard Model. The measured number of light neutrino families was three as expected and the absence of an excess of events beyond that predicted by the Standard Model processes was used to set limits on new physics. Both model independent searches and searches for new processes predicted by supersymmetric and extra-dimensional models have been made. Limits on new non-standard model interactions between neutrinos and electrons were also determined.

A study has been made of the production of single photons in the reaction e+e− → γ + invisible particles at √s = 183 GeV and 189 GeV and a previous analysis of events with a single non-pointing photon or with multi-photon final states accompanied by missing energy has been updated with 189 GeV data. The data was collected with the DELPHI detector and corresponds to an integrated luminosity of about 51 pb−1 and 158 pb−1 at the two energies. The number of light neutrino families is measured. The absence of an excess of events beyond that expected from Standard Model processes is used to set limits on new physics as described by supersymmetric and composite models. A limit on the gravitational scale is also determined. 1 Universita e Sezione INFN, Milano, Italy. 2 Lund University, Lund, Sweden. 3 Universita e Sezione INFN, Bologna, Italy. 4 Universita e Sezione INFN, Padova, Italy. 5 CERN, Geneva, Switzerland. 6 Universite Claude Bernard de Lyon IPNL, Lyon, France.

The inclusive direct and cascade semileptonic branching ratios of the b quark were measured from a fit to the lepton momentum spectrum in the B-hadron rest frame, exploiting the charge correlation between the lepton and the heavy meson. The value of the Vcb element in the CKM quark mixing matrix was computed from the differential decay width of the process B0--> D+-* l- nu, measured as a function of the product W of the B and D* 4-velocities, using an inclusive method of D* reconstruction. A measurement of the ratio Vub/Vcb has been obtained by using the reconstructed secondary hadronic mass in semileptonic decays of B hadrons. The charm semileptonic branching ratio was measured using a double tag method based on the detection of exclusively reconstructed D mesons accompanied by a lepton in the opposite hemisphere.

A novel technique for longitudinal segmentation of shashlik calorimeters has been tested in the CERN West Area beam facility. A 25 tower e.m. calorimeter has been built with vacuum photodiodes inserted in the first 8 radiation lengths to sample the initial development of the shower. Performance in terms of energy resolution, impact point reconstruction and eπ separation are reported.