1,698 research outputs found
Strangeness Production at the HERA-B Experiment
No full textHERA-B is a fixed target experiment at the 920 GeV HERA proton beam at DESY which uses a variety of nuclear targets. During the last data taking period from Nov. 2002 to Feb. 2003, 200 million minimum bias events were recorded. A large sample of V^0(K_zero, Lambda_zero, Lambda_zero_bar), approximately 20000 cascade hyperons Xi^(-/+) and 1200 Omega^(-/+) over low background were reconstructed using these data. About 1 million K^*(892) --> K pi and 60,000 phi(1020) --> K^+K^- decays in central production $(-0.15 < x_F < 0.1, 0.5 < p_t^2 < 12.1 (GeV/c)^2 were analyzed. Preliminary results for differential p_t^2 spectra, atomic numeber dependence and anti-particle to particle ratios are presented
Hyperon production with and neutrons in hyperon experiment WA89 at CERN
No full textInclusive differential cross sections for hyperon production in high- energy Sigma /sup -/, pi /sup -/ and neutron induced interactions are measured by the experiment WA89 at CERN. Secondary Sigma /sup -/ and pi /sup -/ beams with 9 produced by Sigma /sup -/. The influence of the target mass on hyperon cross section is explored by comparing reactions on copper and carbon nuclei. (21 refs)
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)
Studies of production in the forward region at LHCb
No full textLHCb experiment performs a multiple studies at 0.9TeV and 7TeV proton-proton interactions. Results on Energy flow, charge particle multiplicities, particle production ratios, charm production studies are presented and discussed. The comparison with the predictions of different models indicates that more efforts are needed for better understanding of physical processes
Strange particle production with and neutrons in hyperon experiment WA89 at CERN
No full textInclusive differential cross sections for 19 strange particles production in high-energy Sigma /sup -/C, pi /sup -/ and neutron induced interactions are measured by the experiment WA89 at CERN. Secondary Sigma /sup -/ and pi /sup -/ beams with average momenta of 343 GeV/c and a neutron beam of 260 GeV/c were produced by primary protons of 450 GeV/c from the CERN SPS. A strong leading effect is seen for hyperons produced by Sigma /sup -/. At p/sub t//sup 2/ values above 1 (GeV/c)/sup 2/ the differential production cross- section shows a marked increase compared to the usually observed Gaussian behaviour of d sigma /dp/sub t//sup 2/. The important observation was done about the "non-thermal" behavior of the p/sub t //sup 2/ spectrum of the strange particles produced. Comprehensive studies were done for V/sup 0/V/sup 0/ pair production in one event. A clear observation of a different production mechanism of two Lambda /sup 0/ in the same event is the most remarkable result of pair production study. (14 refs)
Measurement of the effective B0s→K+K− lifetime
No full textA measurement of the effective lifetime is presented using approximately 37 pb−1 of data collected by LHCb during 2010. This quantity can be used to put constraints on contributions from processes beyond the Standard Model in the meson system and is determined by two complementary approaches as
τKK=1.440±0.096 (stat)±0.008 (syst)±0.003 (model) ps
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 effective B_s^0 -> J/ψ K_S^0 lifetime
No full textThis paper reports the first measurement of the effective B_s^0 -> J/{\psi} K_S^0 lifetime and an updated measurement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of 1.0 fb^{-1} of pp collisions, recorded by the LHCb experiment in 2011 at a centre-of-mass energy of 7 TeV. The results are: tau_J/{\psi}K_S^0 = 1.75 +/- 0.12 (stat) +/- 0.07 (syst) and BR(B_s^0 -> J/{\psi} K_S^0) = (1.97 +/- 0.23) X 10^{-5}.
For the latter measurement, the uncertainty includes both statistical and systematic sources
Inclusive and production in -nucleus interactions at GeV
No full textCharmonium production by 350~GeV/ negative pions incident on tungsten, copper and silicon has been studied in the WA92 experiment. \jp\ and \pp\ mesons are identified through their decays into muon pairs and are selected in the Feynman- range . Inclusive \jp\ and \pp\ cross-sections and \jp\ differential cross-sections as functions of and are measured. Assuming the relation \sigma = \msz \, A^\alpha between the nuclear cross-section, , and the atomic mass, , of a target nucleus a fit to \jp\ data for different targets yields . Taking , the cross-sections per nucleon for \jp\ and \pp\ are \mszj = 216 \pm 5 \pm 13 \; \mbox{nb} and \mszpp = 28 \pm 8 \pm 11 \; \mbox{nb}, and their ratio is \mszpp / \mszj = 0.13 \pm 0.05 \pm 0.01 . The measurements of charmonium production are compared with results on open-charm production previously obtained in the same experiment. The ratio between the \jp\ cross-section and the charmed-meson cross-section, relating to the same experimental conditions, is found to be $\mszj / \sigma_{0}(D\bar{D}) = (1.75 \pm 0.05 \pm 0.15) \times 10^{-2}.
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