τ LEPTON PHYSICS

1998 ◽  
Vol 13 (05) ◽  
pp. 695-739 ◽  
Author(s):  
GHITA RAHAL-CALLOT
Keyword(s):  
Neutral Current ◽  
Branching Fractions ◽  
New Physics ◽  
Precise Determination ◽  
Energy Scale ◽  
Hadronic Decay ◽  
Charged Current ◽  
Beyond The Standard Model ◽  
Decay Channels

General properties of the τ leptons are reviewed using the recent measurements of production and decay of τ leptons. The improvements in the knowledge of the τ mass and the limits on ντ mass are reported. New improved measurements of the τ polarization and asymmetries performed at LEP and SLC prove a measurement of the axial and vector part of the neutral current at the per mil level. For the leptonic charged current, no deviation from the V–A Lorentz structure of the current is observed. Improvements on the lifetime and leptonic branching fractions allow a check of the charged current universality at the 0.5% level. New hadronic decay channels have been measured, mainly those involving kaons and η mesons. A precise determination of αs at the τ mass energy scale is performed. Finally, tests of possible new physics beyond the Standard Model are discussed.

scholarly journals Multimessenger Probes for New Physics in Light of A. Sakharov’s Legacy in Cosmoparticle Physics

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 222
Author(s):  
Maxim Khlopov
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
New Physics ◽  
Physical Models ◽  
Beyond The Standard Model ◽  
Fundamental Relationship ◽  
Relationship Of ◽  
The Universe ◽  
Selection Of

A.D. Sakharov’s legacy in now standard model of the Universe is not reduced to baryosynthesis but extends to the foundation of cosmoparticle physics, which studies the fundamental relationship of cosmology and particle physics. Development of cosmoparticle physics involves cross-disciplinary physical, astrophysical and cosmological studies of physics Beyond the Standard model (BSM) of elementary particles. To probe physical models for inflation, baryosynthesis and dark matter cosmoparticle physics pays special attention to model dependent messengers of the corresponding models, making their tests possible. Positive evidence for such exotic phenomena as nuclear interacting dark atoms, primordial black holes or antimatter globular cluster in our galaxy would provide the selection of viable BSM models determination of their parameters.

scholarly journals QUARK MIXING AND CP VIOLATION — THE CKM MATRIX

2006 ◽  
Vol 21 (08n09) ◽  
pp. 1724-1737 ◽  
Author(s):  
ULRICH NIERSTE
Keyword(s):  
Neutral Current ◽  
New Physics ◽  
Tree Level ◽  
B Decays ◽  
Ckm Matrix ◽  
Penguin Decays ◽  
The Status ◽  
First Results ◽  
Global Fit

I summarize the theoretical progress in the determination of the CKM elements since Lepton-Photon 2003 and present the status of the elements and parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. One finds |Vus| = 0.2227 ± 0.0017 from K and τ decays and |Vcb| = (41.6 ± 0.5) · 10-3 from inclusive semileptonic B decays. The unitarity triangle can now be determined from tree-level quantities alone and the result agrees well with the global fit including flavour-changing neutral current (FCNC) processes, which are sensitive to new physics. From the global fit one finds the three CKM angles θ12 = 12.9° ± 0.1°, θ23 = 2.38° ± 0.03° and θ13 = 0.223° ± 0.007° in the standard PDG convention. The CP phase equals [Formula: see text] at 1σ CL and [Formula: see text] at 2σ CL. A major progress are first results from fully unquenched lattice QCD computations for the hadronic quantities entering the UT fit. I further present the calculation of three-loop QCD corrections to the charm contribution in [Formula: see text] decays, which removes the last relevant theoretical uncertainty from the [Formula: see text] system. Finally I discuss mixing-induced CP asymmetries in [Formula: see text] penguin decays, whose naive average is below its Standard Model value by 3σ.

scholarly journals CKM PARAMETERS AND RARE B DECAYS

2006 ◽  
Vol 21 (08n09) ◽  
pp. 1683-1696 ◽  
Author(s):  
FRANCESCO FORTI
Keyword(s):  
B Meson ◽  
New Physics ◽  
Precise Determination ◽  
Model Parameters ◽  
B Decays ◽  
Unitarity Triangle ◽  
Indirect Determination ◽  
Radiative Transitions ◽  
First Time

Measurements of the angles and sides of the unitarity triangle and of the rates of rare B meson decays are crucial for the precise determination of Standard Model parameters and are sensitive to the presence of new physics particles in the loop diagrams. In this paper the recent measurements performed in this area by BABAR and Belle will be presented. The direct measurement of the angle α is for the first time as precise as the indirect determination. The precision of the |Vub| determination has improved significantly with respect to previous measurement. New limits on B → τν decays are presented, as well as updated measurements on b → s radiative transitions and a new observation of b → dγ transition made by Belle.

scholarly journals RADIATIVE AND ELECTROWEAK RARE B DECAYS

2004 ◽  
Vol 19 (06) ◽  
pp. 934-948 ◽  
Author(s):  
M. NAKAO
Keyword(s):  
B Meson ◽  
Dominant Role ◽  
Rare Decay ◽  
Neutral Current ◽  
New Physics ◽  
Beyond The Standard Model ◽  
B Meson Decays ◽  
Meson Decays ◽  
Flavor Changing ◽  
Flavor Changing Neutral Current

This report summarizes the latest experimental results on radiative and electroweak rare B meson decays. These rare decay processes proceed through the Flavor-Changing-Neutral-Current processes, and thus are sensitive to the postulated new particles in the theories beyond the Standard Model. Experiments at e+e- colliders, Belle, BaBar and CLEO, have been playing the dominant role, while the CDF and D0 experiments have just started to provide new results from Tevatron Run-II. The most significant achievement is the first observation of the decay B→K*ℓ+ℓ-, which opens a new window to search for new physics in B meson decays.

scholarly journals LEPTONIC UNIVERSALITY BREAKING IN ϒ DECAYS AS A PROBE OF NEW PHYSICS

2004 ◽  
Vol 19 (13) ◽  
pp. 2183-2206 ◽  
Author(s):  
MIGUEL ANGEL SANCHIS-LOZANO
Keyword(s):  
Higgs Boson ◽  
Branching Fractions ◽  
New Physics ◽  
Partial Width ◽  
Dipole Transition ◽  
Beyond The Standard Model ◽  
Color Singlet ◽  
Lepton Universality ◽  
Fock State ◽  
The Standard Model

In this work, we examine the possible existence of new physics beyond the standard model which could modify the branching fractions of the leptonic (mainly tauonic) decays of bottomonium vector resonances below the [Formula: see text] threshold. The decay width is factorized as the product of two pieces: (a) the probability of an intermediate pseudoscalar color-singlet [Formula: see text] state (coupling to the dominant Fock state of the Upsilon via a magnetic dipole transition) and a soft (undetected) photon; (b) the annihilation width of the [Formula: see text] pair into two leptons, mediated by a non-standard CP-odd Higgs boson of mass about 10 GeV, introducing a quadratic dependence on the lepton mass in the partial width. The process would be unwittingly ascribed to the ϒ leptonic channel thereby (slightly) breaking lepton universality. A possible mixing of the pseudoscalar Higgs and bottomonium resonances is also considered. Finally, several experimental signatures to check out the validity of the conjecture are discussed.

scholarly journals CP VIOLATION AND A SEARCH FOR NEW PHYSICS IN LHCb

2007 ◽  
Vol 22 (31) ◽  
pp. 5973-5985 ◽  
Author(s):  
◽  
LESLIE CAMILLERI
Keyword(s):  
Cp Violation ◽  
B Physics ◽  
New Physics ◽  
Precise Determination ◽  
Particle Identification ◽  
Production Rates ◽  
Ckm Matrix ◽  
Physics Program ◽  
Physics Experiment

The physics program of LHCb concerns the study of CP violation in the B system, including more precise determination of the CKM matrix parameters and in particular the determination of φs The search for new physics which could manifest itself indirectly will be a high priority. The main advantages of LHCb over the B factories are the access to the Bs system and very large B production rates. In addition, LHCb is a dedicated B physics experiment with excellent vertexing and particle identification capabilities. It is currently setting up its detector in its allocated LHC interaction region and is foreseen to be ready for data taking in November 2007 for the pilot run.

scholarly journals Search for K+ → π+νν̅ at NA62

2018 ◽  
Vol 182 ◽  
pp. 02002
Author(s):  
Riccardo Aliberti
Keyword(s):  
Standard Model ◽  
Rare Decay ◽  
New Physics ◽  
Energy Scale ◽  
Beyond The Standard Model ◽  
Fixed Target ◽  
The Standard Model ◽  
Target Experiment ◽  
Flavour Physics ◽  
Fixed Target Experiment

Flavour physics is one of the most powerful fields for the search of new physics beyond the Standard Model. The kaon sector with the rare decay K+ → π+νν̅ provides one of the cleanest and most promising channels. NA62, a fixed target experiment at the CERN SPS, aims to measure BR (K+ → π+νν̅) with 10% precision to test the Standard Model validity up to an energy scale of hundreds of TeV. NA62 had dedicated data taking for the K+ → π+νν̅ measurement in 2016 and 2017 and will continue in 2018. Here preliminary results on a fraction of 2016 dataset are presented. The analysis of the complete 2016 data sample is expected to achieve the SM sensitivity.

scholarly journals IMPACT OF THE BOUNDS ON HIGGS MASS AND mW ON EFFECTIVE THEORIES

2000 ◽  
Vol 15 (21) ◽  
pp. 1377-1384 ◽  
Author(s):  
J. L. DIAZ-CRUZ ◽  
J. M. HERNANDEZ ◽  
J. J. TOSCANO
Keyword(s):  
Higgs Mass ◽  
New Physics ◽  
Precise Determination ◽  
Lagrangian Approach ◽  
Radiative Corrections ◽  
Effective Parameters ◽  
Effective Lagrangian ◽  
Effective Theories

We study the inter-relations that exist between the present experimental bounds on the Higgs mass, as obtained from radiative corrections to mW, and the effective parameters, αi and Λ. We find that the SM bounds on mH, arising from a precise determination of the W mass, can be substantially modified by the presence of dimension-six operators which appear in the linear realization of the effective Lagrangian approach. A Higgs mass as heavy as 700 GeV can be allowed for scales of new physics of the order of 1 TeV.

scholarly journals Probing lepton universality with (semi)-leptonic B decays

2019 ◽  
Author(s):  
Giovanni Banelli ◽  
Robert Fleischer ◽  
Ruben Jaarsma ◽  
Gilberto Tetlalmatzi-Xolocotzi
Keyword(s):  
Standard Model ◽  
Branching Fraction ◽  
Branching Fractions ◽  
Belle Collaboration ◽  
New Physics ◽  
Recent Measurement ◽  
Beyond The Standard Model ◽  
Lepton Universality ◽  
Highly Sensitive ◽  
The Standard Model

The most recent measurements of the observables R_{D^{(*)}}RD(*) are in tension with the Standard Model offering hints of New Physics in b\rightarrow c \ell \bar{\nu}_{\ell}b→cℓν‾ℓ transitions. Motivated by these results, in this work we present an analysis on their b\rightarrow u \ell \bar{\nu}_{\ell}b→uℓν‾ℓ counterparts (for \ell=e, ~\mu, ~\tauℓ=e,μ,τ). Our study has three main objectives. Firstly, using ratios of branching fractions, we assess the effects of beyond the Standard Model scalar and pseudoscalar particles in leptonic and semileptonic BB decays (B^-\rightarrow \ell^- \bar{\nu}_{\ell}B−→ℓ−ν‾ℓ, \bar{B}\rightarrow \pi \ell \bar{\nu}_{\ell}B‾→πℓν‾ℓ and \bar{B}\rightarrow \rho \ell \bar{\nu}_{\ell}B‾→ρℓν‾ℓ). Here a key role is played by the leptonic BB processes, which are highly sensitive to new pseudoscalar interactions. In particular, we take advantage of the most recent measurement of the branching fraction of the channel B^-\rightarrow \mu^-\bar{\nu}_{\mu}B−→μ−ν‾μ by the Belle collaboration. Secondly, we extract the CKM matrix element |V_{ub}||Vub| while accounting simultaneously for New Physics contributions. Finally, we provide predictions for the branching fractions of yet unmeasured leptonic and semileptonic BB decays.

scholarly journals B decay anomalies at LHCb

2018 ◽  
Vol 175 ◽  
pp. 01004
Author(s):  
Arantza Oyanguren
Keyword(s):  
Standard Model ◽  
B Meson ◽  
Neutral Current ◽  
New Physics ◽  
Lhcb Collaboration ◽  
Beyond The Standard Model ◽  
Clear Tendency ◽  
The Standard Model ◽  
Model Predictions ◽  
Lepton Flavour

The LHCb collaboration has provided a plethora of precise measurements of flavour observables in the last years. In the B meson sector some of these results show consistent deviations from Standard Model predictions with a clear tendency to specific New Physics scenarios. B decay anomalies are found in particular related to lepton flavour universality tests and angular observables in Flavour-Changing-Neutral-Current transitions. I review here the LHCb measurements and their experimental caveats. Results from Lattice are crucial in the coming years to verify if these anomalies are explained by QCD effects or if they are unambiguous hints of physics beyond the Standard Model.

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