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Observation of the $\Lambda_b^0\to\Lambda\phi$ decay
Physics Letters B. 2016. Vol. 759. P. 282.
The Λb0→Λϕ decay is observed using data corresponding to an integrated luminosity of 3.0 fb−1 recorded by the LHCb experiment. The decay proceeds at leading order via a b→ss‾s loop transition and is therefore sensitive to the possible presence of particles beyond the Standard Model. A first observation is reported with a significance of 5.9 standard deviations. The value of the branching fraction is measured to be (5.18±1.04±0.35−0.62+0.67)×10−6 , where the first uncertainty is statistical, the second is systematic, and the third is related to external inputs. Triple-product asymmetries are measured to be consistent with zero.
Keywords: high energy physics
Aushev T., Mizuk R., Pakhlov P. et al., Physical Review Letters 2020 P. 1-15
We report results from a study of the spin and parity of Ξc(2970)+ using a 980 fb−1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. The decay angle distributions in the chain Ξc(2970)+→Ξc(2645)0π+→Ξ+cπ−π+ are analyzed to determine the spin of this charmed-strange baryon. The angular distributions strongly favor the Ξc(2970)+ spin ...
Added: November 27, 2020
Aaij R., Boldyrev A., Derkach D. et al., Physical Review D - Particles, Fields, Gravitation and Cosmology 2021 Vol. 104 No. 5 Article 052010
A search for CP violation in charmless three-body Ξ−b→pK−K− decays is performed using pp collision data recorded with the LHCb detector, corresponding to integrated luminosities of 1 fb−1 at a center-of-mass energy √s=7 TeV, 2 fb−1 at √s=8 TeV and 2 fb−1 at √s=13 TeV. A good description of the phase-space distribution is obtained with an amplitude model containing contributions from Σ(1385), Λ(1405), Λ(1520), Λ(1670), Σ(1775) and Σ(1915) resonances. The model allows for CP -violation effects, which are found to be consistent with zero. The branching fractions ...
Added: March 18, 2022
Aaij R., Abellán Beteta C., Ackernley T. et al., Chinese Physics C 2021 Vol. 45 No. 9 Article 093002
The first search for the doubly heavy Ω0bc baryon and a search for Ξ0bc baryon are performed using pp collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.2fb−1. The baryons are reconstructed via their decays to Λ+cπ− and Ξ+cπ−. No significant excess is found for invariant masses between 6700 and ...
Added: March 18, 2022
V.Belavin, A.Filatov, A.Ustyuzhanin et al., Journal of Physics: Conference Series 2018 Vol. 1085 No. 4 P. 042025-1-042025-6
Traces of electro-magnetic showers in the neutrino experiments may be considered as signals of dark-matter particles. For example, SHiP experiment is going to use emulsion film detectors similar to the ones designed for OPERA experiment from dark matter search. The goal of this research is to develop an algorithm that can identify traces of electro-magnetic ...
Added: December 8, 2017
Aushev T., Mizuk R., Pakhlov P. et al., Physical Review D - Particles, Fields, Gravitation and Cosmology 2019 Vol. 99 No. 11 P. 1-8
We report a search for X(3872) and X(3915) in B+→χc1π0K+ decays. We set an upper limit of B(B+→X(3872)K+)×B(X(3872)→χc1π0) <8.1×10−6 and B(B+→X(3915)K+)×B(X(3915)→χc1π0) <3.8×10−5 at 90\% confidence level. We also measure B(X(3872)→χc1π0)/B(X(3872)→J/ψπ+π−)<0.97 at 90\% confidence level. The results reported here are obtained from 772×106 BB¯¯¯¯ events collected at the Υ(4S) resonance with the Belle detector at the ...
Added: June 5, 2020
Aaij R., Arzymatov K., Belavin V. et al., Science Bulletin 2021 Vol. 66 No. 13 P. 1278-1287
First evidence of a structure in the J/ψΛ invariant mass distribution is obtained from an amplitude analysis of Ξb-→J/ψΛK- decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1σ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be 4458.8±2.9-1.1+4.7MeV and 17.3±6.5-5.7+8.0MeV, respectively, where the quoted uncertainties are statistical ...
Added: August 28, 2021
Yelton J., Aushev T., Mizuk R. et al., Physical Review D - Particles, Fields, Gravitation and Cosmology 2020 Article 071103(R
Using 980 fb−1 of data collected with the Belle detector operating at the KEKB asymmetric-energy e^+e^- collider, we report a study of the electromagnetic decays of excited {charmed baryons} Ξc(2790) and Ξc(2815). A clear signal (8.6 standard deviations) is observed for Ξc(2815)0→Ξ0cγ, and we measure:
B[Ξc(2815)0→Ξ0cγ]/B[Ξc(2815)0→Ξc(2645)+π−→Ξ0cπ+π−]=0.41±0.05±0.03.
We also present evidence (3.8 standard deviations) for the similar decay ...
Added: November 27, 2020
Mizuk R., Aushev T., Pakhlov P. et al., Journal of High Energy Physics 2019 P. 1-30
We report a new measurement of the e+e−→Υ(nS)π+π− (n=1,2,3) cross sections at energies from 10.52 to 11.02 GeV using data collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are ...
Added: June 5, 2020
Aaij R., Beteta C. A., A. Boldyrev et al., Journal of High Energy Physics 2020 Vol. 02 No. 049 P. 1-17
A measurement of the Ξ++cc mass is performed using data collected by the LHCb experiment between 2016 and 2018 in pppp collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.6 fb−1fb−1. The Ξ++cc candidates are reconstructed via the decay modes Ξ++cc→Λ+cK−π+π+ and Ξ++cc→Ξ+cπ+. The result, 3621.55±0.23(stat)±0.30(syst)MeV/c2, is the most precise measurement of the Ξ++cc mass to date. ...
Added: September 16, 2020
Aaij R., Beteta C. A., Boldyrev A. et al., Science Bulletin 2020 Vol. 65 No. 23 P. 1983-1993
Using proton-proton collision data at centre-of-mass energies of s=7,8 and 13TeV recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9fb-1, the invariant mass spectrum of J/ψ pairs is studied. A narrow structure around 6.9GeV/c2 matching the lineshape of a resonance and a broad structure just above twice the J/ψ mass are observed. The deviation of the data from ...
Added: September 17, 2020
Aaij R., Beteta C. A., A. Boldyrev et al., Journal of High Energy Physics 2020 Vol. 11 No. 095 P. 1-20
A search for the doubly heavy {\Xi}_{bc}^0Ξbc0 baryon using its decay to the D^{0}0pK^{–}– final state is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the LHCb experiment between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb^{−1}−1. No significant signal is found in the invariant mass range from 6.7 ...
Added: December 2, 2020
Aaij R., Abdelmotteleb A. S., Abellán Beteta C. et al., Journal of Instrumentation 2022 Vol. 17 Article P02028
The identification of charm jets is achieved at LHCb for data collected in 2015–2018 using a method based on the properties of displaced vertices reconstructed and matched with jets. The performance of this method is determined using a dijet calibration dataset recorded by the LHCb detector and selected such that the jets are unbiased in ...
Added: December 28, 2022
The LHCb C., Boldyrev A., Derkach D. et al., Journal of High Energy Physics 2020 Vol. 2020 No. 6 Article 110
This paper presents an analysis of the Λ0𝑏Λb0→ J/ψΛ angular distribution and the transverse production polarisation of Λ0𝑏Λb0 baryons in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The measurements are performed using data corresponding to an integrated luminosity of 4.9 fb−1, collected with the LHCb experiment. The polarisation is determined in a fiducial region ...
Added: September 17, 2020
Kazeev N., Ustyuzhanin A., Artemov A. et al., Journal of Physics: Conference Series 2015 Vol. 664 No. 3 P. 032019-032019
During LHC Run 1, the LHCb experiment recorded around 1011 collision events. This paper describes Event Index — an event search system. Its primary function is to quickly select subsets of events from a combination of conditions, such as the estimated decay channel or number of hits in a subdetector. Event Index is essentially Apache ...
Added: October 24, 2016
Aushev T., Pakhlova G., Углов Т. В. et al., Journal of High Energy Physics 2021
Using a data sample of 980 fb−1 collected with the Belle detector at the KEKB asymmetric-energy e+e− collider, we study the processes of Ξ0c→ΛK¯∗0, Ξ0c→Σ0K¯∗0, and Ξ0c→Σ+K∗− for the first time. The relative branching ratios to the normalization mode of Ξ0c→Ξ−π+ are measured to be
{\cal
B}(\Xi^0_c\to \Lambda\bar K^{*0})/{\cal B}(\xic\to \Xi^-\pi^+)=0.18\pm0.02({\rm
stat.})\pm0.01({\rm syst.}),
{\cal B}(\Xi^0_c\to \Sigma^0\bar K^{*0})/{\cal
B}(\xic\to \Xi^-\pi^+)=0.69\pm0.03({\rm stat.})\pm0.03({\rm syst.}),
{\cal
B}(\Xi^0_c\to \Sigma^+K^{*-})/{\cal B}(\xic\to \Xi^-\pi^+)=0.34\pm0.06({\rm
stat.})\pm0.02({\rm syst.}),
where the uncertainties are statistical and systematic, respectively. We obtain %measure the branching fractions of Ξ0c→ΛK¯∗0, Ξ0c→Σ0K¯∗0, and Ξ0c→Σ+K∗− to be
(Ξ0c→ΛK¯∗0)=(3.3±0.3(stat.)±0.2(syst.)±1.0(ref.))×10−3,
(Ξ0c→Σ0K¯∗0)=(12.4±0.5(stat.)±0.5(syst.)±3.6(ref.))×10−3,
(Ξ0c→Σ+K∗−)=(6.1±1.0(stat.)±0.4(syst.)±1.8(ref.))×10−3,
where the uncertainties are ...
Added: December 16, 2021
The LHCb collaboration -., Aaij R., Abdelmotteleb A. S. et al., Journal of High Energy Physics 2021 Article 107
A search for the doubly charmed baryon 𝛯+𝑐𝑐Ξcc+ is performed in the 𝛯+𝑐𝜋−𝜋+Ξc+π−π+ invariant-mass spectrum, where the 𝛯+𝑐Ξc+ baryon is reconstructed in the pK−π+ final state. The study uses proton-proton collision data collected with the LHCb detector at a centre- of-mass energy of 13 TeV, corresponding to a total integrated luminosity of 5.4 fb−1. No significant signal is observed in the invariant-mass range ...
Added: March 2, 2022
Aaij R., Abdelmotteleb A. S., Abellán Beteta C. et al., Journal of High Energy Physics 2022 Vol. 2022 No. 5 Article 38
The Ξ++ → Ξ′+π+ decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4fb−1. The Ξ++ → Ξ′+π+ decay is reconstructed partially, where the photon from the Ξ′+ → Ξ+γ decay is not reconstructed and the pK−π+ final state of the ...
Added: December 30, 2022
A S Boldyrev, A Maevsky, Journal of Physics: Conference Series 2017 Vol. 798 No. 1 P. 1-5
Towards the end of LHC Run1, gas leaks were observed in some parts of the Transition Radiation Tracker (TRT) of ATLAS. Due to these leaks, primary Xenon based gas mixture was replaced with Argon based mixture in various parts. Test-beam studies with a dedicated Transition Radiation Detector (TRD) prototype were carried out in 2015 in ...
Added: January 30, 2019
LHCb C., Derkach D., Kazeev N. et al., Physical Review Letters 2017 Vol. 119 No. 18 P. 181807-1-181807-9
A search for baryon-number violating Ξb0 oscillations is performed with a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 3 fb−1. The baryon number at the moment of production is identified by requiring that the Ξb0 come from the decay of a resonance Ξb*−→Ξb0π− or Ξb′−→Ξb0π−, and the ...
Added: November 23, 2017
Aaij R., Abdelmotteleb A. S., Abellán Beteta C. et al., Physical Review Letters 2022 Vol. 129 No. 9 Article 091801
The first study of the angular distribution of μþμ− pairs produced in the forward rapidity region via the Drell-Yan reaction pp → γ=Z þ X → lþl− þ X is presented, using data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb−1. The coefficients ...
Added: December 29, 2022
Aaij R., Arzymatov K., Belavin V. et al., Physical Review Letters 2021 Vol. 126 No. 16 Article 161802
We present an angular analysis of the Bþ → Kþð→ K0SπþÞμþμ− decay using 9 fb−1 of pp collision data collected with the LHCb experiment. For the first time, the full set of CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B0 → K0μþμ− decay. The global tension ...
Added: August 28, 2021
Aaij R., Arzymatov K., Belavin V. et al., Physical Review Letters 2021 Vol. 126 No. 9 Article 091802
A measurement of CP violation in the decay B+→K+π0 is reported using data corresponding to an integrated luminosity of 5.4 fb−1 collected with the LHCb experiment at a center-of-mass energy of √s=13 TeV. The CP asymmetry is measured to be 0.025±0.015±0.006±0.003, where the uncertainties are statistical, systematic, and due to an external input. This is the most precise measurement of this quantity. It confirms and significantly enhances ...
Added: August 28, 2021
Aaij R., Abdelmotteleb A. S., Abellán Beteta C. et al., Physical Review Letters 2022 Vol. 128 No. 19 Article 191803
The first observation of the semileptonic b-baryon decay Λ0b→Λ+cτ−¯ντ, with a significance of 6.1σ, is reported using a data sample corresponding to 3 fb−1 of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The τ− lepton is reconstructed in the hadronic decay to three charged pions. The ratio K=B(Λ0b→Λ+cτ−¯ντ)/B(Λ0b→Λ+cπ−π+π−) is measured to be 2.46±0.27±0.40, where the first ...
Added: December 28, 2022
The LHCb c., A. Boldyrev, D. Derkach et al., Journal of High Energy Physics 2020 Vol. 03 Article 147
The decay-time-dependent CP asymmetry in B0→D∗±D∓ decays is measured using a data set corresponding to an integrated luminosity of 9fb−1 recorded by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The CP parameters are measured as
SD∗D=−0.861±0.077(stat)±0.019(syst),
ΔSD∗D=0.019±0.075(stat)±0.012(syst),
CD∗D=−0.059±0.092(stat)±0.020(syst),
ΔCD∗D=−0.031±0.092(stat)±0.016(syst),
D∗D=0.008±0.014(stat)±0.006(syst).
The analysis provides the most precise single measurement of CP violation in this decay channel to date. All parameters are consistent with their ...
Added: September 16, 2020