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Search for the rare decay Λ c+→ p μ+ μ−
Physical Review D - Particles, Fields, Gravitation and Cosmology. 2018. Vol. 97. P. 091101-1-091101-10.
A search for the flavor-changing neutral-current decay Λ c+→ p μ+ μ− is reported using a
data set corresponding to an integrated luminosity of 3.0 fb− 1 collected by the LHCb
Collaboration. No significant signal is observed outside of the dimuon mass regions around
the ϕ and ω resonances, and an upper limit is placed on the branching fraction of B (Λ c+→
p μ+ μ−)< 7.7 (9.6)× 10− 8 at 90%(95%) confidence level. A significant signal is observed in
the ω dimuon mass region for the first time.
Aaij R., Belavin V., Boldyrev A. et al., Physics Letters B 2021 No. 815 Article 136172
The Λ0b→Λ+cK+K−π−Λb0→Λc+K+K−π− decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of s√=7s=7 and 8 TeVTeV collected by the LHCbLHCb detector, corresponding to an integrated luminosity of 3fb−13fb−1. The ratio of branching fractions between the Λ0b→Λ+cK+K−π−Λb0→Λc+K+K−π− and the Λ0b→Λ+cD−sΛb0→Λc+Ds− decays is measured to be
B(Λ0b→Λ+cK+K−π−)B(Λ0b→Λ+cD−s)=(9.26±0.29±0.46±0.26)×10−2,B(Λb0→Λc+K+K−π−)B(Λb0→Λc+Ds−)=(9.26±0.29±0.46±0.26)×10−2,
where the first uncertainty is statistical, the second systematic and the third is due to the knowledge ...
Added: August 31, 2021
Aaij R., Beteta C. A., Boldyrev A. et al., Journal of High Energy Physics 2021 Vol. 2021 No. 3 P. 1-45
The CKM angle γγ is measured for the first time from mixing-induced CPCP violation between B0s→D∓sK±π±π∓Bs0→Ds∓K±π±π∓ and B¯0s→D±sK∓π∓π±B¯s0→Ds±K∓π∓π± decays reconstructed in proton-proton collision data corresponding to an integrated luminosity of 9 fb−1fb−1 recorded with the LHCb detector. A time-dependent amplitude analysis is performed to extract the CPCP-violating weak phase γ−2βsγ−2βs and, subsequently, γγ by taking the B0sBs0-B¯0sB¯s0 mixing phase βsβs as an external input. The measurement yields γ=(44±12)∘γ=(44±12)∘ modulo 180∘180∘, where statistical and systematic uncertainties are combined. ...
Added: August 31, 2021
Aaij R., Beteta C. A., Boldyrev A. et al., Physical Review Letters 2021 Vol. 126 No. 12 P. 1-11
Using pppp collision data corresponding to an integrated luminosity of 5.4fb−15.4fb−1 collected with the LHCb detector at a center-of-mass energy of 13TeV13TeV, the B0→D−D+K+π−B0→D−D+K+π− decay is studied. A new excited D+sDs+ meson is observed decaying into the D+K+π−D+K+π− final state with large statistical significance. The pole mass and width, and the spin-parity of the new state are measured with an amplitude analysis to be mR=2591±6±7MeVmR=2591±6±7MeV, ΓR=89±16±12MeVΓR=89±16±12MeV and JP=0−JP=0−, where the ...
Added: August 31, 2021
Aaij R., Arzymatov K., Baranov A. et al., The European Physical Journal C - Particles and Fields 2020 Vol. 80 Article 986
A first search for CPCP violation in the Cabibbo-suppressed Ξ+c→pK−π+Ξc+→pK−π+ decay is performed using both a binned and an unbinned model-independent technique in the Dalitz plot. The studies are based on a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0fb−13.0fb−1, and collected by the LHCb experiment at centre-of-mass energies of 7 and 8TeV8TeV. The data are consistent ...
Added: December 7, 2020
Aaij R., Beteta C. A., Boldyrev A. et al., The European Physical Journal C - Particles and Fields 2021 Vol. 81 No. 261 P. 1-16
Long-lived particles decaying to e±μ∓νe±μ∓ν, with masses between 7 and 5050 GeV/c22 and lifetimes between 2 and 5050 ps, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using 5.45.4 fb−1−1 of pppp collisions collected with the LHCb detector at a centre-of-mass energy of s√=13s=13 TeV. Three mechanisms of production of long-lived particles are considered: the direct pair ...
Added: August 31, 2021
Hushchyn M., Ustyuzhanin A., Derkach D. et al., Physics Letters B 2017 Vol. 767 P. 177-187
A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D0→K−K+ is performed using pp collision data, corresponding to an integrated luminosity of 3fb−1, collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The flavour of the charm meson at production is determined from the charge of the pion in ⁎D⁎+→D0π+ and ⁎D⁎−→D‾0π− decays. The time-integrated CP asymmetry ACP(K−K+) is obtained assuming negligible CP violation in charm ...
Added: January 30, 2018
Ryzhikov A., Ustyuzhanin A., Journal of Physics: Conference Series 2018 Vol. 1085 P. 1-6
In the research, a new approach for finding rare events in high-energy physics was tested. As an example of physics channel the decay of \tau -> 3 \mu is taken that has been published on Kaggle within LHCb-supported challenge. The training sample consists of simulated signal and real background, so the challenge is to train ...
Added: December 11, 2017
Derkach D., Hushchyn M., Kazeev N. et al., Physical Review Letters 2019 Vol. 123 No. 3 P. 1-11
The radiative decay Λ0b→Λγ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of 1.7 fb−1 collected by the LHCb experiment at a center-of-mass energy of 13 TeV. Its branching fraction is measured exploiting the B0→K*0γ decay as a normalization mode and is found to be B(Λ0b→Λγ)=(7.1±1.5±0.6±0.7)×10−6, where the quoted uncertainties are statistical, systematic, and ...
Added: March 16, 2020
M. Borisyak, N. Kazeev, Journal of Instrumentation 2019 Vol. 14 No. 08 P. 1-8
Data analysis in high energy physics often deals with data samples consisting of a mixture of signal and background events. The sPlot technique is a common method to subtract the contribution of the background by assigning weights to events. Part of the weights are by design negative. Negative weights lead to the divergence of some ...
Added: August 20, 2019
Ustyuzhanin A., Likhomanenko T., Derkach D. et al., Journal of Instrumentation 2016 Vol. 11
A new algorithm for the determination of the initial flavour of B0 s mesons is presented. The algorithm is based on two neural networks and exploits the b hadron production mechanism at a hadron collider. The first network is trained to select charged kaons produced in association with the B0 s meson. The second network ...
Added: October 23, 2016
Сапронов А. А., Aad G., Glazov A., Journal of High Energy Physics 2017 Vol. 1710 No. 182 P. 1-60
A search is conducted for new resonant and non-resonant high-mass phenomena in dielectron and dimuon final states. The search uses 36.1 fb−1 of proton-proton collision data, collected at s√=13 TeV by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the Standard Model prediction is observed. Upper limits at 95% ...
Added: August 7, 2018
Hushchyn M., Derkach D., Ustyuzhanin A. et al., Physics Letters B 2018 Vol. 777 P. 16-30
Measurements of CP observables in B±→D(⁎)K± and B±→D(⁎)π± decays are presented, where D(⁎) indicates a neutral D or D⁎ meson that is an admixture of D(⁎)0 and D¯(⁎)0states. Decays of the D⁎ meson to the Dπ0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the Bcandidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K±π∓, K+K− and π+π− final states. The analysis uses a sample of charged B mesons ...
Added: January 30, 2018
Borisyak M., Ustyuzhanin A., Derkach D. et al., Journal of Physics: Conference Series 2017 No. 898 P. 1-7
High-energy physics experiments rely on reconstruction of the trajectories of particles produced at the interaction point. This is a challenging task, especially in the high track multiplicity environment generated by p-p collisions at the LHC energies. A typical event includes hundreds of signal examples (interesting decays) and a significant amount of noise (uninteresting examples). This ...
Added: June 16, 2017
Borisyak M., Ustyuzhanin A., Ratnikov F. et al., Physical Review Letters 2017 Vol. 118 No. 19 P. 191801-1-191801-11
A search for the rare decays Bs0→μ+μ- and B0→μ+μ- is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb-1. An excess of Bs0→μ+μ- decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The ...
Added: October 22, 2017
Derkach D., Borisyak M., Ustyuzhanin A. et al., Physics Letters B 2016 No. 762 P. 253-262
A time-dependent angular analysis of Bs0→ψ(2S)ϕ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0fb−1 collected during Run 1 of the LHC. The CP -violating phase and decay-width difference of the Bs0 system are measured to be ϕs=0.23−0.28+0.29±0.02rad and ΔΓs=0.066−0.044+0.041±0.007ps−1 , respectively, where the ...
Added: October 21, 2016
Aaboud M., Glazov A., et a. et al., The European Physical Journal C - Particles and Fields 2016 Vol. 76 No. 12 P. 1-42
he algorithms used by the ATLAS Collaboration to reconstruct and identify prompt photons are described. Measurements of the photon identification efficiencies are reported, using 4.9 fb−1 of pp collision data collected at the LHC at s√=7 TeV and 20.3 fb−1 at s√=8 TeV . The efficiencies are measured separately for converted and unconverted photons, in ...
Added: August 7, 2018
Aaij R., Beteta C. A., Borisyak M. et al., Physical Review Letters 2020 Vol. 124 No. 4 P. 1-12
Searches are performed for both prompt-like and long-lived dark photons, A′, produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for A′→μ+μ− decays using a data sample corresponding to an integrated luminosity of 5.5/fb collected with the LHCb detector. Neither search finds evidence for a signal, and 90 confidence-level exclusion ...
Added: September 16, 2020
Ustyuzhanin A., Likhomanenko T., Derkach D. et al., Journal of High Energy Physics 2016
The decays Λb0 → ψ(2S)pK− and Λb0 → J/ψπ+π−pK− are observed in a data sample corresponding to an integrated luminosity of 3 fb−1, collected in proton-proton collisions at 7 and 8 TeV centre-of-mass energies by the LHCb detector. The ψ(2S) mesons are reconstructed through the decay modes ψ(2S) → μ+μ− and ψ(2S) → J/ψπ+π−.
The branching fractions relative to that of Λb0 → J/ψpK− are measured to be
M(Λ0b)=5619.65±0.17±0.17 MeV/c2,M(Λb0)=5619.65±0.17±0.17 MeV/c2, ...
Added: October 23, 2016
Aaij R., Boldyrev A., Beteta C. A. et al., Physical Review Letters 2020 Vol. 124 No. 3 P. 031801
Observations are reported of different sources of CP violation from an amplitude analysis of B+→π+π+π− decays, based on a data sample corresponding to an integrated luminosity of 3 fb−1 of pp collisions recorded with the LHCb detector. A large CP asymmetry is observed in the decay amplitude involving the tensor f2(1270) resonance, and in addition significant CP violation is found in the π+π−S wave at low invariant mass. The presence of CP violation related ...
Added: December 7, 2020
Borisyak M., Belous M., Derkach D. et al., Journal of Instrumentation 2017
High-energy physics experiments rely on reconstruction of the trajectories of particles produced at the interaction point. This is a challenging task, especially in the high track multiplicity environment generated by p-p collisions at the LHC energies. A typical event includes hundreds of signal examples (interesting decays) and a significant amount of noise (uninteresting examples). This ...
Added: October 18, 2017
Derkach D., Hushchyn M., Likhomanenko T. et al., Journal of Physics: Conference Series 2018 Vol. 1085 No. 4 P. 1-5
One of the most important aspects of data analysis at the LHC experiments is the particle identification (PID). In LHCb, several different sub-detectors provide PID information: two Ring Imaging Cherenkov (RICH) detectors, the hadronic and electromagnetic calorimeters, and the muon chambers. To improve charged particle identification, we have developed models based on deep learning and ...
Added: October 18, 2018
Derkach D., Hushchyn M., Kazeev N. et al., Journal of High Energy Physics 2019 Vol. 6 P. 1-27
The first untagged decay-time-integrated amplitude analysis of Bs0 → KS0K±π∓ decays is performed using a sample corresponding to 3.0 fb−1 of pp collision data recorded with the LHCb detector during 2011 and 2012. The data are described with an amplitude model that contains contributions from the intermediate resonances K*(892)0,+, K2*(1430)0,+ and K0*(1430)0,+, and their charge conjugates. Measurements of the branching fractions of the decay modes Bs0 → K*(892)±K∓ and 𝐵0𝑠→𝐾∗(---)(892)0𝐾0(---)Bs0→K∗(---)(892)0K0(---) are in ...
Added: March 16, 2020
Сапронов А. А., Aad G., Glazov A., Physical Review D - Particles, Fields, Gravitation and Cosmology 2017 Vol. 96 No. 7 P. 072002-1-072002-36
Jet energy scale measurements and their systematic uncertainties are reported for jets measured with the ATLAS detector using proton-proton collision data with a center-of-mass energy of s=13 TeV, corresponding to an integrated luminosity of 3.2 fb-1 collected during 2015 at the LHC. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells, using the anti-kt ...
Added: August 7, 2018
Borisyak M., Ratnikov F., Ustyuzhanin A., Physical Review Letters 2017 Vol. 118 No. 25 P. 251802-251812
A search for the rare decays Bs0→τ+τ- and B0→τ+τ- is performed using proton–proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3 fb-1 collected in 2011 and 2012. The τ leptons are reconstructed through the decay τ-→π-π+π-ντ. Assuming no contribution from B0→τ+τ- decays, an upper limit is set ...
Added: October 22, 2017