scholarly journals Recent results on B → μ+μ− decays with the CMS experiment

2020 ◽  
Vol 35 (34) ◽  
pp. 2030017
Author(s):  
Urs Langenegger
Keyword(s):  
Maximum Likelihood ◽  
Confidence Level ◽  
Particle Physics ◽  
Branching Fraction ◽  
Identification Algorithm ◽  
Effective Lifetime ◽  
Cms Experiment ◽  
Upper Limit ◽  
The Standard Model ◽  
Fragmentation Probability

Results on [Formula: see text] decays with the CMS experiment are reported, using 61 fb[Formula: see text] of data recorded during LHC Run 1 and 2016. With an improved muon identification algorithm and refined unbinned maximum likelihood fitting methods, the decay [Formula: see text] is observed with a significance of 5.6 standard deviations. Its branching fraction is measured to be [Formula: see text], where the first error is the combined statistical and systematic uncertainty and the second error quantifies the uncertainty of the [Formula: see text] and [Formula: see text] fragmentation probability ratio. The [Formula: see text] effective lifetime is [Formula: see text]. No evidence for the decay [Formula: see text] is found and an upper limit of [Formula: see text] (at 95% confidence level) is determined. All results are consistent with the standard model of particle physics.

scholarly journals Search for dark photons in Higgs boson production via vector boson fusion in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
T. Bergauer ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Fraction ◽  
Vector Boson ◽  
Boson Mass ◽  
Higgs Boson Mass ◽  
Vector Boson Fusion ◽  
Upper Limit ◽  
The Standard Model

Abstract A search is presented for a Higgs boson that is produced via vector boson fusion and that decays to an undetected particle and an isolated photon. The search is performed by the CMS collaboration at the LHC, using a data set corresponding to an integrated luminosity of 130 fb−1, recorded at a center-of-mass energy of 13 TeV in 2016–2018. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for production via vector boson fusion and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a Higgs boson mass of 125 GeV, assuming the standard model production rates, the observed (expected) 95% confidence level upper limit on the branching fraction is 3.5 (2.8)%. This is the first search for such decays in the vector boson fusion channel. Combination with a previous search for Higgs bosons produced in association with a Z boson results in an observed (expected) upper limit on the branching fraction of 2.9 (2.1)% at 95% confidence level.

scholarly journals Search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c.

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
◽  
M. Ablikim ◽  
M. N. Achasov ◽  
P. Adlarson ◽  
S. Ahmed ◽  
...  
Keyword(s):  
Confidence Level ◽  
Branching Fraction ◽  
Center Of Mass ◽  
Leptonic Decay ◽  
Mass Energy ◽  
Center Of Mass Energy ◽  
Upper Limit ◽  
Electron Positron

Abstract Using 10.1 × 109J/ψ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $$ \sqrt{s} $$ s = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction ℬ(J/ψ → D−e+νe + c. c.) < 7.1 × 10−8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

A SEARCH FOR THE DECAY B+ → τ+ντ AT BABAR

2005 ◽  
Vol 20 (16) ◽  
pp. 3695-3697
Author(s):  
◽  
MOUSUMI DATTA
Keyword(s):  
Confidence Level ◽  
Branching Fraction ◽  
Upper Limit ◽  
B Factory ◽  
Babar Detector

We present a search for the decay B+ → τ+ντ in [Formula: see text] decays recorded with the BABAR detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay [Formula: see text] is selected, and in the recoil a search for B+ → τ+ ντ signal is performed. The τ is identified in the following channels: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]. We find no evidence of signal, and we set a preliminary upper limit on the branching fraction of [Formula: see text] at the 90% confidence level (CL). This result is then combined with a statistically independent BABAR search for B+ → τ+ντ to give a combined preliminary limit of [Formula: see text] at 90% CL.

SEARCH FOR THE DECAY Bs→μ+μ -ϕ IN $p\bar p$ COLLISIONS AT $\sqrt{s} =1.8\, {\rm TeV}$

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 461-463
Author(s):  
◽  
THOMAS SPEER
Keyword(s):  
Confidence Level ◽  
Branching Fraction ◽  
Neutral Current ◽  
Current Decay ◽  
Flavor Changing ◽  
Upper Limit ◽  
Flavor Changing Neutral Current ◽  
Neutral Current Decay

We present a search for the flavor-changing neutral current decay Bs→ μ+μ-ϕ in [Formula: see text] collisions at [Formula: see text], using 91.4 pb-1 of data collected at the Collider Detector at Fermilab (CDF). We find two candicate events for this decay, which is consistent with the background estimate, and set a preliminary upper limit on the branching fraction of ℬ(Bs → μ+ μ-ϕ)<4.2 · 10-5 at a 90% confidence level.

scholarly journals Latest Belle results on Tau decays

2019 ◽  
Author(s):  
Yifan Jin ◽  
Denis Epifanov ◽  
Hiroaki Aihara
Keyword(s):  
Confidence Level ◽  
Branching Fraction ◽  
Data Set ◽  
Tau Decays ◽  
Preliminary Results ◽  
Upper Limit

We present preliminary results of a latest measurement at Belle, the branching fraction of rare tau decay, \tau^- \rightarrow \pi^- \nu_{\tau} \ell^+ \ell^-τ−→π−ντℓ+ℓ− (\ell = eℓ=e or \muμ), using a 562 \rm fb^{-1} data set. The branching fraction of \tau^- \rightarrow \pi^- e^+ e^- \nu_\tauτ−→π−e+e−ντ is measured to be \mathbf{ \mathcal{B}(\tau^-\rightarrow \pi^- e^+ e^- \nu_\tau) = (2.11 \pm 0.19 \pm 0.30) \times 10^{-5}}ℬ(𝛕−→𝛑−𝐞+𝐞−𝛎𝛕)=(2.11±0.19±0.30)×10−5, where the first uncertainty is statistical and the second is systematic. An upper limit is set on the branching fraction of \tau^- \rightarrow \pi^- \mu^+ \mu^- \nu_\tauτ−→π−μ+μ−ντ, \mathbf{\mathcal{B}(\tau^-\rightarrow \pi^- \mu^+ \mu^- \nu_\tau) < 1.06 \times 10^{-5}}ℬ(𝛕−→𝛑−𝛍+𝛍−𝛎𝛕)<1.06×10−5, at 90% confidence level.

scholarly journals Dark photon search at Yemilab, Korea

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
S. H. Seo ◽  
Y. D. Kim
Keyword(s):  
Electron Beam ◽  
Confidence Level ◽  
Particle Physics ◽  
Absorption Process ◽  
Neutrino Detector ◽  
Dark Sector ◽  
Dark Photon ◽  
Mixing Parameter ◽  
The Standard Model ◽  
Background Events

Abstract Dark photons are well motivated hypothetical dark sector particles that could account for observations that cannot be explained by the standard model of particle physics. A search for dark photons that are produced by an electron beam striking a thick tungsten target and subsequently interact in a 3 kiloton-scale neutrino detector in Yemilab, a new underground lab in Korea, is proposed. Dark photons can be produced by “darkstrahlung” or by oscillations from ordinary photons produced in the target and detected by their visible decays, “absorption” or by their oscillation to ordinary photons. By detecting the absorption process or the oscillation-produced photons, a world’s best sensitivity for measurements of the dark-photon kinetic mixing parameter of ϵ2> 1.5 × 10−13(6.1 × 10−13) at the 95% confidence level (C.L.) could be obtained for dark photon masses between 80 eV and 1 MeV in a year-long exposure to a 100 MeV–100 kW electron beam with zero (103) background events. In parallel, the detection of e+e− pairs from decays of dark photons with mass between 1 MeV and ∼86 MeV would have sensitivities of ϵ2>$$ \mathcal{O}\left({10}^{-17}\right)\left(\mathcal{O}\left({10}^{-16}\right)\right) $$ O 10 − 17 O 10 − 16 at the 95% C.L. with zero (103) background events. This is comparable to that of the Super-K experiment under the same zero background assumption.

RECENT RESULTS FROM ARGUS

1993 ◽  
Vol 08 (07) ◽  
pp. 573-582 ◽  
Author(s):  
HENNING SCHRÖDER
Keyword(s):  
Standard Model ◽  
Storage Ring ◽  
Confidence Level ◽  
Fundamental Constants ◽  
Matrix Elements ◽  
B Decays ◽  
Ckm Matrix ◽  
Upper Limit ◽  
The Standard Model ◽  
Yukawa Sector

Using the ARGUS detector at the e+e− storage ring DORIS II at DESY new results on beauty and τ physics have been obtained. In particular, new measurements on fundamental constants in the Yukawa sector of the Standard Model are presented. These comprise measurements of CKM matrix elements from the study of B decays as well as determinations of properties of the τ lepton and its neutrino vτ. From semileptonic B decays ARGUS finds |Vcb|=0.050±0.008±0.007 and from [Formula: see text] mixing |Vtd|= 0.007±0.002. An analysis of the decay type τ−→π−π−π+ντ yields a τ mass of mτ=(1776.3±2.4±1.4) MeV/c2. This result also leads to an improvement of the upper limit on the [Formula: see text] at the 95% confidence level.

A SEARCH FOR B→τν

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 636-638 ◽  
Author(s):  
◽  
JOHN GREGG THAYER
Keyword(s):  
Confidence Level ◽  
B Meson ◽  
Branching Fraction ◽  
Slight Modification ◽  
B Meson Decays ◽  
Meson Decays ◽  
Decay Modes ◽  
Upper Limit ◽  
Charged B Meson

We report results of a search for B→τν in a sample of 9.7 million charged B meson decays. The search uses both πν and [Formula: see text] decay modes of the τ, and demands exclusive reconstruction of the companion [Formula: see text] decay to suppress background. We set an upper limit on the branching fraction ℬ(B→τν)<8.4×10-4 at 90% confidence level. With slight modification to the analysis we also establish [Formula: see text] at 90% confidence level.

scholarly journals Search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ = 13 TeV

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
W Boson ◽  
Branching Fraction ◽  
Heavy Flavor ◽  
Significant Excess ◽  
Proton Proton ◽  
Proton Collisions ◽  
Lepton Flavor ◽  
Cms Experiment ◽  
Upper Limit ◽  
Proton Proton Collisions

Abstract Results are reported from a search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ s = 13 TeV. The data sample corresponds to an integrated luminosity of 33.2 fb−1 recorded by the CMS experiment at the LHC in 2016. The search exploits τ leptons produced in both W boson and heavy-flavor hadron decays. No significant excess above the expected background is observed. An upper limit on the branching fraction ℬ(τ → 3μ) of 8.0 × 10−8 at 90% confidence level is obtained, with an expected upper limit of 6.9 × 10−8.

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