اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدObservation of double charm production involving open charm in pp collisions at $sqrt{s}$=7 TeV
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The production of $J/psi$ mesons accompanied by open charm, and of pairs of open charm hadrons are observed in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of $355pb^{-1}$ collected with the LHCb detector. Model independent measurements of absolute cross-sections are given together with ratios to the measured $J/psi$ and open charm cross-sections. The properties of these events are studied and compared to theoretical predictions.
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Charm production at the LHC in pp collisions at sqrt(s)=7 TeV is studied with the LHCb detector. The decays D0 -> K- pi+, D+ -> K- pi+ pi+, D*+ -> D0(K- pi+) pi+, D_s+ -> phi(K- K+) pi+, Lambda_c+ -> p K- pi+, and their charge conjugates are analysed
in a data set corresponding to an integrated luminosity of 15 nb^{-1}. Differential cross-sections dsigma/dp_T are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0 < p_T < 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 p_T-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives sigma(cbar{c})_{p_T < 8 GeV/c, 2.0 < y < 4.5} = 1419 +/- 12 (stat) +/- 116 (syst) +/- 65 (frag) microbarn, where the uncertainties are statistical, systematic, and due to the fragmentation functions.
Associated production of bottomonia and open charm hadrons in $pp$ collisions at $sqrt{s}=7$ and $8$TeV is observed using data corresponding to an integrated luminosity of 3$fb^{-1}$ accumulated with the LHCb detector. The observation of five combina
tions, $Upsilon(1S)D^0$, $Upsilon(2S)D^0$, $Upsilon(1S)D^+$, $Upsilon(2S)D^+$ and $Upsilon(1S)D^+_{s}$, is reported. Production cross-sections are measured for $Upsilon(1S)D^0$ and $Upsilon(1S)D^+$ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism. This allows a precise measurement of the effective cross-section for double parton scattering.
Using 34.7 pb-1 of data collected with the LHCb detector, the inclusive production of the X(3872) meson in pp collisions at sqrt(s) = 7 TeV is observed for the first time. Candidates are selected in the X(3872) -> J/psi pi+ pi- decay mode, and used t
o measure sigma(pp -> X(3872) + anything) B(X(3872)-> J/psi pi+ pi-) = 5.4 +- 1.3 (stat) +- 0.8 (syst) nb, where sigma(pp -> X(3872) + anything) is the inclusive production cross-section of X(3872) mesons with rapidity in the range 2.5-4.5 and transverse momentum in the range 5-20 GeV/c. In addition the masses of both the X(3872) and psi(2S) mesons, reconstructed in the J/psi pi+ pi- final state, are measured to be m(X(3872)) = 3871.95 +- 0.48 (stat) +- 0.12 (syst) MeV/c2 and m(psi(2S)) = 3686.12 +- 0.06 (stat) +- 0.10 (syst) MeV/c2
Production cross-sections of prompt charm mesons are measured using data from $pp$ collisions at the LHC at a centre-of-mass energy of $5,$TeV. The data sample corresponds to an integrated luminosity of $8.60pm0.33,$pb$^{-1}$ collected by the LHCb ex
periment. The production cross-sections of $D^0$, $D^+$, $D_s^+$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{text{T}}$, and rapidity, $y$. They cover the rapidity range $2.0<y<4.5$ and transverse momentum ranges $0 < p_{text{T}} < 10, text{GeV}/c$ for $D^0$ and $D^+$ and $1 < p_{text{T}} < 10, text{GeV}/c$ for $D_s^+$ and $D^{*+}$ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of $1 < p_{text{T}} < 8, text{GeV}/c$ are determined to be sigma(pprightarrow D^0 X) = 1004 pm 3 pm 54,mutext{b} sigma(pprightarrow D^+ X) = 402 pm 2 pm 30,mutext{b} sigma(pprightarrow D_s^+ X) = 170 pm 4 pm 16,mutext{b} sigma(pprightarrow D^{*+} X)= 421 pm 5 pm 36,mutext{b} where the uncertainties are statistical and systematic, respectively.
The production of $J/psi$ pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of $37.5 pb^{-1}$ collected with the LHCb detector. The production cross-section for pairs with both jpsi
in the rapidity range $2<y^{J/psi}<4.5$ and transverse momentum $p_{T}^{J/psi}<10 GeV/c$ is $$ sigma^{J/psi J/psi} = 5.1pm1.0pm1.1 nb,$$ where the first uncertainty is statistical and the second systematic.
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