The Large Hadron Collider beauty (LHCb) experiment at CERN is undergoing an upgrade in preparation for the Run 3 data collection period at the Large Hadron Collider (LHC). As part of this upgrade, ...the trigger is moving to a full software implementation operating at the LHC bunch crossing rate. We present an evaluation of a CPU-based and a GPU-based implementation of the first stage of the high-level trigger. After a detailed comparison, both options are found to be viable. This document summarizes the performance and implementation details of these options, the outcome of which has led to the choice of the GPU-based implementation as the baseline.
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Observation of the decay → J/ψ K+K−π Adinolfi, M.; Albrecht, J.; Anderlini, L. ...
The journal of high energy physics,
12/11, Volume:
2013, Issue:
11
Journal Article
Peer reviewed
Open access
A
bstract
The decay
→
J/ψK
+
K
−
π
+
is observed for the first time, using protonproton collisions collected with the LHCb detector corresponding to an integrated luminosity of 3 fb
−1
. A signal ...yield of 78 ± 14 decays is reported with a significance of 6.2 standard deviations. The ratio of the branching fraction of
→
J/ψK
+
K
−
π
+
decays to that of
→
J/ψπ
+
decays is measured to be 0
.
53 ± 0
.
10 ± 0
.
05, where the first uncertainty is statistical and the second is systematic.
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LHCb, while purpose built for \(b-\)physics, also functions as a general purpose forward detector, covering the pseudo-rapidity range 2.0 to 5.0. LHCb has performed several measurements including ...jets, which concern, e.g., QCD, top and Higgs physics. A selection of LHCb results in this area will be presented, focusing on the most recent ones.
A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of 3 fb super(-1) collected ...at centre-of-mass energies of 7 and 8 TeV, J/psiJ/psi and J/psipsi(2S) pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges (-3.5, -1.5) and (1.5, 5.0). Searches are also performed for pairs of P-wave charmonia and limits are set on their production. The cross-sections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measured to be sigma super(J/psiJ/psi) = 58 + or - 10(stat) + or - 6(syst) pb, sigma super(J/psipsi(2S)) = (ProQuest: Formulae and/or non-USASCII text omitted) + or - 10(syst) pb, sigma super(psi(2S)psi(2S)) < 237 pb, sigma super( chi c0 chi c0) < 69 nb, sigma super( chi c1 chi c1) < 45 pb, sigma super( chi c2 chi c2) < 141 pb, where the upper limits are set at the 90% confidence level. The measured J/psiJ/psi and J/psipsi/(2S) cross-sections are consistent with theoretical expectations.
The charged-particle production ratios p¯/p, K −/K +, π −/π +, (p+p¯)/(π++π−), (K ++K −)/(π ++π −) and (p+p¯)/(K++K−) are measured with the LHCb detector using 0.3 nb−1 of pp collisions delivered by ...the LHC at s√=0.9 TeV and 1.8 nb−1 at s√=7 TeV. The measurements are performed as a function of transverse momentum p T and pseudorapidity η. The production ratios are compared to the predictions of several Monte Carlo generator settings, none of which are able to describe adequately all observables. The ratio p¯/p is also considered as a function of rapidity loss, Δy≡y beam−y, and is used to constrain models of baryon transport.
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The production of B ± mesons in proton-proton collisions at s√ = 7 TeV is studied using 35 pb−1 of data collected by the LHCb detector. The B ± mesons are reconstructed exclusively in the B ± → J/ψK ...± mode, with J/ψ → μ + μ −. The differential production cross-section is measured as a function of the B ± transverse momentum in the fiducial region 0 < p T < 40 GeV/c and with rapidity 2.0 < y < 4.5. The total cross-section, summing up B + and B −, is measured to be σ(pp → B ± X, 0 < p T < 40 GeV/c, 2.0 < y < 4.5) = 41.4 ± 1.5 (stat.) ± 3.1 (syst.) μb.
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Evidence for the hadronic annihilation decay mode B+→D+sϕ is found with greater than 3σ significance. The branching fraction and CP asymmetry are measured to be $ ...B(B+→D+sϕ)=(1.87+1.25−0.73(stat)±0.19(syst)±0.32(norm))×10−6,ACP(B+→D+sϕ)=−0.01±0.41(stat)±0.03(syst). $ The last uncertainty on B(B+→D+sϕ) is from the branching fractions of the B+→D+sD¯¯¯0 normalization mode and intermediate resonance decays. Upper limits are also set for the branching fractions of the related decay modes B+(c)→D+(s)K∗0,B+(c)→D+(s)K¯¯¯∗0 and B+c→D+sϕ , including the result B(B+→D+K∗0)<1.8×10−6 at the 90% credibility level.
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The LHCb experiment at CERN is undergoing an upgrade in preparation for the Run 3 data taking period of the LHC. As part of this upgrade the trigger is moving to a fully software implementation ...operating at the LHC bunch crossing rate. We present an evaluation of a CPU-based and a GPU-based implementation of the first stage of the High Level Trigger. After a detailed comparison both options are found to be viable. This document summarizes the performance and implementation details of these options, the outcome of which has led to the choice of the GPU-based implementation as the baseline.
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