1,961 research outputs found
Prompt charm production in pp collisions at √<span style="text-decoration:overline">s</span>=7 TeV
No full textCharm production at the LHC in pp collisions at s√=7 TeV is studied with the LHCb detector. The decays D0→K−π+, D+→K−π+π+, D⁎+→D0(K−π+)π+, D+s→ϕ(K−K+)π+, Λ+c→pK−π+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb−1. Differential cross-sections dσ/dpT are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0<pT<8 GeV/c and 2.0<y<4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above pT-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives
σ(cc¯)pT<8 GeV/c,2.0<y<4.5=1419±12(stat)±116(syst)±65(frag) μb,
where the uncertainties are statistical, systematic, and due to the fragmentation functions
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
First observations of B̅[0 over s]→D[superscript +]D[superscript -], D[+ over s]D[superscript -] and D[superscript 0]D̅[superscript 0] decays
No full textFirst observations and measurements of the branching fractions of the B̅[0 over s]→D[superscript +]D[superscript -], B̅[0 over s]→D[+ over s]D[superscript -] and B̅[0 over s]→D[superscript 0]D̅[superscript 0] decays are presented using 1.0 fb[superscript -1] of data collected by the LHCb experiment. These branching fractions are normalized to those of B̅[superscript 0]→D[superscript +]D[superscript -], B[superscript 0]→D[superscript -]D[+ over s] and B[superscript -]→D[superscript 0]D[- over s], respectively. An excess of events consistent with the decay B̅[superscript 0]→D[superscript 0]D̅[superscript 0] is also seen, and its branching fraction is measured relative to that of B[superscript -]→D[superscript 0]D[- over s]. Improved measurements of the branching fractions B(B̅[0 over s]→D[+ over s]D[- over s]) and B(B[superscript -]→D[superscript 0]D[- over s]) are reported, each relative to B(B[superscript 0]→D[superscript -]D[+ over s]). The ratios of branching fractions are B(B̅[0 over s]→D[superscript +]D[superscript -])/B(B̅[superscript 0]→D[superscript +]D[superscript -])=1.08±0.20±0.10, B(B̅[0 over s]→D[+ over s]D[superscript -])/B(B[superscript 0]→D[superscript -]D[+ over s])=0.050±0.008±0.004, B(B̅[0 over s]→D[superscript 0]D̅[superscript 0])/B(B[superscript -]→D[superscript 0]D[- over s])=0.019±0.003±0.003, B(B̅[superscript 0]→D[superscript 0]D̅[superscript 0])/B(B[superscript -]→D[superscript 0]D[- over s])<0.0024 at 90% CL, B(B̅[0 over s]→D[+ over s]D[- over s])/B(B[superscript 0]→D[superscript -]D[+ over s])=0.56±0.03±0.04, B(B[superscript -]→D[superscript 0]D[- over s])/B(B[superscript 0]→D[superscript -]D[+ over s])=1.22±0.02±0.07, where the uncertainties are statistical and systematic, respectively.National Science Foundation (U.S.
Observations of Bºs→ψ(2S)η and Bº(s)→ψ(2S)π+π- decays
No full textFirst observations of the B0s
→ψ(2S)η, B0 →ψ(2S)π
+
π
− and B0s
→ψ(2S)π
+
π
− decays are made
using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in
proton–proton collisions at a centre-of-mass energy of
√
s = 7 TeV. The ratios of the branching fractions
of each of the ψ(2S) modes with respect to the corresponding J/ψ decays are
B(B0s
→ψ(2S)η)
÷
B(B0s
→J/ψη)
= 0.83± 0.14 (stat)±0.12 (syst) ±0.02 (B),
;
B(B0→ψ(2S)π
+
π
−
)
÷
B(B0→J/ψπ
+
π
−
)
= 0.56± 0.07 (stat)±0.05 (syst)± 0.01 (B),
;
B(B0s
→ψ(2S)π
+
π
−
)
÷
B(B0s
→J/ψπ
+
π
−
)
= 0.34± 0.04 (stat)±0.03 (syst)± 0.01 (B),
where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/ψ
and ψ(2S) meson decays
Measurement of the B0–B0 oscillation frequency Δmd with the decays B0→D−π+ and B0→ J/ψK∗0
No full textThe B
0
–B
0
oscillation frequency Δmd is measured by the LHCb experiment using a dataset corresponding
to an integrated luminosity of 1.0 fb−1
of proton–proton collisions at √
s = 7 TeV, and is found to be
Δmd
=0.5156±0.0051 (stat.)±0.0033 (syst.) ps−1
. The measurement is based on results from analyses
of the decays B
0
→ D
−π
+ (D
−
→ K
+π
−π
−) and B
0
→ J/ψK
∗0
(J/ψ →μ
+μ
−,K
∗0
→ K
+π
−) and
their charge conjugated modes
Measurements of the branching fractions of the decays B0s→D∓sK± and B0s→D−sπ+
No full textThe decay mode B0s→D∓sK± allows for one of the theoretically cleanest measurements of the CKM angle γ through the study of time-dependent CP violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode B0s→D−sπ+ based on a data sample corresponding to 0.37 fb−1 of proton-proton collisions at s√=7TeV collected in 2011 with the LHCb detector. In addition, the ratio of B meson production fractions f s /f d , determined from semileptonic decays, together with the known branching fraction of the control channel B 0 → D −π+, is used to perform an absolute measurement of the branching fractions: B(B0s→D−sπ+)=(2.95±0.05±0.17+0.18−0.22)×10−3,\hfillB(B0s→D∓sK±)=(1.90±0.12±0.13+0.12−0.14)×10−4,\hfill where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to f s /f d
Measurement of D∗±, D± and D±s meson production cross sections in pp collisions at √s= 7 TeV with the ATLAS detector
No full textThe production of D∗±, D± and D±s charmed mesons has been measured with the ATLAS detector in pp collisions at √s= 7 TeV at the LHC, using data corresponding to an integrated luminosity of 280 nb−1. The charmed mesons have been reconstructed in the range of transverse momentum 3.5 <pT(D) <100 GeV and pseudorapidity |η(D)| <2.1. The differential cross sections as a function of transverse momentum and pseudorapidity were measured for D∗± and D± production. The next-to-leading-order QCD predictions are consistent with the data in the visible kinematic region within the large theoretical uncertainties. Using the visible D cross sections and an extrapolation to the full kinematic phase space, the strangeness-suppression factor in charm fragmentation, the fraction of charged non-strange D mesons produced in a vector state, and the total cross section of charm production at √s= 7 TeV were derived
Search for D+(s) to pi+ mu+ mu- and D+(s) to pi- mu+ mu+ decays
No full textA search for non-resonant D+(s) to pi+mu+mu- and D+(s) to pi-mu+mu+ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb-1, at sqrt(s) = 7 TeV recorded by the LHCb experiment in 2011. No signals are observed and the 90% (95%) confidence level (CL) limits on the branching fractions are B(D+ to pi+mu+mu-) < 7.3 (8.3) x 10-8, B(Ds+ to pi+mu+mu-) < 4.1 (4.8) x 10-7, B(D+ to pi-mu+mu+) < 2.2 (2.5) x 10-8, B(Ds+ to pi-mu+mu+) < 1.2 (1.4) x 10-7. These limits are the most stringent to date
Study of DsJ decays to D+KS0 and D0K+ final states in pp collisions
No full textA study of D+K0S and D0K+ final states is performed in a sample of 1.0 fb−1 of pp collision data collected at a centre-of-mass energy of s√=7 TeV with the LHCb detector. We confirm the existence of the D∗s1(2700)+ and D∗sJ(2860)+ excited states and measure their masses and widths to be
m(D∗s1(2700)+) = 2709.2±1.9(stat)±4.5(syst) MeV/c2, Γ(D∗s1(2700)+) = 115.8±7.3(stat)±12.1(syst) MeV/c2, m(D∗sJ(2860)+) = 2866.1±1.0(stat)±6.3(syst) MeV/c2, Γ(D∗sJ(2860)+) = 69.9±3.2(stat)±6.6(syst) MeV/c2
Measurement of the D-s(+)-D-s(-) production asymmetry in 7 TeV pp collisions
No full textHeavy quark production in 7 TeV centre-of-mass energy pp collisions at the LHC is not necessarily flavour
symmetric. The production asymmetry, AP, between D
+
s
and D
−
s
mesons is studied using the φπ
± decay
mode in a data sample of 1.0 fb−1
collected with the LHCb detector. The difference between π
+ and
π
− detection efficiencies is determined using the ratios of fully reconstructed to partially reconstructed
D
∗± decays. The overall production asymmetry in the D
±
s
rapidity region 2.0 to 4.5 with transverse
momentum larger than 2 GeV is measured to be AP
=(−0.33±0.22±0.10)%. This result can constrain
models of heavy flavour production
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