Prompt production of charmonium $\chi_{c0}$, $\chi_{c1}$ and $\chi_{c2}$ mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of $\sqrt{s}=7$TeV. The $\chi_{c}$ mesons are identified through their decay to $J/\psi\gamma$, with $J/\psi\to\mu^+\mu^-$ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of $1.0\mathrm{fb}^{-1}$ collected by the LHCb detector, is used to measure the relative prompt production rate of $\chi_{c1}$ and $\chi_{c2}$ in the rapidity range $2.0
Measurements of the ratio of $\chi_{c2}$ to $\chi_{c1}$ production cross-sections for the given $J/\psi$ $p_T$ range assuming unpolarized $\chi_c$ production. The first uncertainty is statistical, the second is systematic, the third is from the branching fractions used and the last gives the maximum correction due to the unknown polarization.
Ratio of $\chi_{c0}$ to $\chi_{c2}$ in the observed $J/\psi$\ $p_T$ range from 4-20 GeV. Also given is the $\chi_{c2}$ to $\chi_{c1}$ ratio in the same PT range for comparison. The first systematic error is dominated by the photon efficiency,the $\chi_{c1}$ tail parameters and background modelling, the third from the choiceof $p_T$ spectrum and the fourth from the branching fraction uncertainty.
Inclusive production cross sections of $\pi^\pm$, $K^\pm$ and $p\bar{p}$ per hadronic $e^+e^-$ annihilation event in $e^+e^-$ are measured at a center-of-mass energy of 10.54 GeV, using a relatively small sample of very high quality data from the BaBar experiment at the PEP-II $B$-factory at the SLAC National Accelerator Laboratory. The drift chamber and Cherenkov detector provide clean samples of identified $\pi^\pm$, $K^\pm$ and $p\bar{p}$ over a wide range of momenta. Since the center-of-mass energy is below the threshold to produce a $B\bar{B}$ pair, with $B$ a bottom-quark meson, these data represent a pure $e^+e^- \rightarrow q\bar{q}$ sample with four quark flavors, and are used to test QCD predictions and hadronization models. Combined with measurements at other energies, in particular at the $Z^0$ resonance, they also provide precise constraints on the scaling properties of the hadronization process over a wide energy range.
Differential cross section for prompt PI+-, K+- and PBAR/P production.
Differential cross section for conventional PI+-, K+- and PBAR/P production.
Integrated cross sections for prompt PI+-, K+- and PBAR/P production. The second (sys) error is the uncertainty due to the model dependence of the extrapolation.
The process e+e- --> p anti-p gamma is studied using 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider, at an e+e- center-of-mass energy of 10.6 GeV. From the analysis of the p anti-p invariant mass spectrum, the energy dependence of the cross section for e+e- --> p anti-p is measured from threshold to 4.5 GeV. The energy dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, and the asymmetry in the proton angular distribution are measured for p anti-p masses below 3 GeV. We also measure the branching fractions for the decays J/psi --> p anti-p and psi(2S) --> p anti p.
Measurement of the cross section as a function of the invariant mass of the PBAR-P system and the effective form factor for the reaction E+ E- --> PBAR P. The contributions from J/PSI and PSI(25) decaying to PBAR-P have been subtracted. The form factor error is the combined statistical and systematic.
The production of \chib1P mesons in $pp$ collisions at a centre-of-mass energy of $7\tev$ is studied using $32\invpb$ of data collected with the \lhcb detector. The $\chib1P$ mesons are reconstructed in the decay mode $\chib1P \to \Y1S\g \to \mumu\g$. The fraction of \Y1S originating from \chib1P decays in the \Y1S transverse momentum range $6 < \pt^{\Y1S} < 15\gevc$ and rapidity range $2.0 < y^{\Y1S} < 4.5$ is measured to be $(20.7\pm 5.7\pm 2.1^{+2.7}_{-5.4})%$, where the first uncertainty is statistical, the second is systematic and the last gives the range of the result due to the unknown \Y1S and \chib1P polarizations.
Fraction of $\Upsilon(1S)$ originating from $\chi_b(1P)$ decays for different $p_T(\Upsilon(1S))$ bins, assuming production of unpolarized $\Upsilon(1S)$ and $\chi_b(1P)$ mesons. The first uncertainty is statistical, the second is the systematic uncertainty ($10.21\%$) and the third uncertainty is due to the unknown $\Upsilon(1S)$ and $\chi_b(1P)$ polarizations ($ _{-26}^{+13}\%$). The second and third uncertainties are considerent constant over the measurement fiducial phase-space.
Direct photons have been measured in sqrt(s_NN)=200 GeV d+Au collisions at midrapidity. A wide p_T range is covered by measurements of nearly-real virtual photons (1<p_T<6 GeV/c) and real photons (5<p_T<16 GeV/c). The invariant yield of the direct photons in d+Au collisions over the scaled p+p cross section is consistent with unity. Theoretical calculations assuming standard cold nuclear matter effects describe the data well for the entire p_T range. This indicates that the large enhancement of direct photons observed in Au+Au collisions for 1.0<p_T<2.5 GeV/c is due to a source other than the initial-state nuclear effects.
Direct photon fraction. The direct-photon fractions from the virtual-photon analysis as a function of $p_{T}$ in $p+p$ (MB) [1] collisions. The values in the table are equal to this mean value. The statistical and systematic uncertainties are shown by the bars and bands, respectively. The curves show expectations from a NLO pQCD calculation [17, 18] with different cutoff mass scales: (solid) $\mu$ = 0.5 $p_{T}$ , (dash) $\mu$ = 1.0 $p_{T}$ , and (dash-dot) $\mu$ = 2.0 $p_{T}$.
Direct photon fraction. The direct-photon fractions from the virtual-photon analysis as a function of $p_{T}$ in $d$+Au (MB) [1] collisions. The values in the table are equal to this mean value. The statistical and systematic uncertainties are shown by the bars and bands, respectively. The curves show expectations from a NLO pQCD calculation [17, 18] with different cutoff mass scales: (solid) $\mu$ = 0.5 $p_{T}$ , (dash) $\mu$ = 1.0 $p_{T}$ , and (dash-dot) $\mu$ = 2.0 $p_{T}$.
Direct photon cross section. (a) The invariant cross sections of the direct photon in $p+p$ [3, 4] and $d$+Au collisions. The $p+p$ fit result with the empirical parameterization described in the text is shown as well as NLO pQCD calculations, and the scaled $p+p$ fit is compared with the $d$+Au data. The closed and open symbols show the results from the virtual photon and $\pi_{0}$-tagging methods, respectively. The asterisk symbols show the result from the statistical subtraction method for $d$+Au data, overlapping with the virtual photon result in 3 < $p_{T}$ < 5 GeV/c. The values in the table are equal to this mean value. The bars and bands represent the point-to-point (ptp.) and $p_{T}$-correlated (cor.) uncertainties, respectively. (b) The $p+p$ data over the fit. The uncertainties of the fit due to both point-to-point (ptp.) and pT -correlated uncertainties of the data are summed quadratically, and the sum is shown as dotted lines. The NLO pQCD calculations divided by the fit are also shown.
We report the measurement of direct photons at midrapidity in Au+Au collisions at sqrt{s_NN} = 200 GeV. The direct photon signal was extracted for the transverse-momentum range of 4 GeV/c < p_T < 22 GeV/c, using a statistical method to subtract decay photons from the inclusive-photon sample. The direct-photon nuclear-modification factor R_AA was calculated as a function of p_T for different Au+Au collision centralities using the measured p+p direct-photon spectrum and compared to theoretical predictions. R_AA was found to be consistent with unity for all centralities over the entire measured p_T range. Theoretical models that account for modifications of initial-direct-photon production due to modified-parton-distribution functions in Au and the different isospin composition of the nuclei, predict a modest change of R_AA from unity and are consistent with the data. Models with compensating effects of the quark-gluon plasma on high-energy photons, such as suppression of jet-fragmentation photons and induced-photon bremsstrahlung from partons traversing the medium, are also consistent with this measurement.
Direct photon spectra for all centrality selections in Au+Au.
Direct photon nuclear modification factor ($R_{AA}$)
A precise measurement of the cross section of the process $e^+e^-\to\pi^+\pi^-(\gamma)$ from threshold to an energy of 3GeV is obtained with the initial-state radiation (ISR) method using 232fb$^{-1}$ of data collected with the BaBar detector at $e^+e^-$ center-of-mass energies near 10.6GeV. The ISR luminosity is determined from a study of the leptonic process $e^+e^-\to\mu^+\mu^-(\gamma)\gamma_{\rm ISR}$, which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process $e^+e^-\to\pi^+\pi^-(\gamma)$ is obtained with a systematic uncertainty of 0.5% in the dominant $\rho$ resonance region. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured $\pi\pi$ cross section from threshold to 1.8GeV is $(514.1 \pm 2.2({\rm stat}) \pm 3.1({\rm syst}))\times 10^{-10}$.
Bare cross-section $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ The cross section values (nb) for 337 CM energy intervals (GeV) from 0.3 to 3 GeV. The cross section is bare (excluding vacuum polarization) and includes the emission of final state photons. ***WARNING*** The quoted errors are from the diagonal elements of the statistical covariance matrix (reported on the Table titled "Bare cross-section statistical covariance") and added quadratically with the systematic uncertainties (reported in the Table titled "Bare cross-section systematic uncertainties"). These errors can be used when plotting the results as they are representative of the precision achieved. However, any calculation involving the cross section over some energy range MUST use, to be meaningful, the full statistical covariance matrix and the proper correlations of the systematic uncertainties. ***WARNING*** The Bare cross-section statistical covariance is reported as additional resource in YAML, since its size exceeds the maximum size of 10 MB for the library hepdata_lib. It is a statistical covariance matrix, for 337x337 CM energy intervals (GeV), from 0.3 to 3 GeV, matching the ones of this table.
Bare cross-section $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ systematic uncertainties contributions and total systematic uncertainties, for 337 CM energy intervals (GeV), from 0.3 to 3 GeV. All systematics contributions are each 100% correlated in all energy bins.
Bare cross-section $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ statistical covariance matrix, for 337x337 CM energy intervals (GeV), from 0.3 to 3 GeV.
The production of B+- mesons in proton-proton collisions at sqrt(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/psi K+- mode, with J/psi -> mu+ mu-. The differential production cross-section is measured as a function of the B+- transverse momentum in the fiducial region 0 < pT < 40 GeV/c and with rapidity 2.0 < y < 4.5. The total cross-section, summing up B+ and B-, is measured to be sigma(pp -> B+- X, 0 < pT < 40 GeV/c, 2.0 < y < 4.5) = 41.4 +- 1.5 (stat.) +- 3.1 (syst.) mub.
Integrated B+- production cross section for 0<PT<40 GeV and 2.0<Y<4.5.
Differential B+- production cross section as a function of PT for rapidity 2.0 to 4.5.
The prompt production of the charmonium $\chi_{c1}$ and $\chi_{c2}$ mesons has been studied in proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The $\chi_c$ mesons are identified through their decays $\chi_c\to J/\psi\,\gamma$ with $J/\psi \to \mu^+ \mu^-$ using 36 $\mathrm{pb^{-1}}$ of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for the two $\chi_c$ spin states, $\sigma(\chi_{c2})/\sigma(\chi_{c1})$, has been determined as a function of the $J/\psi$ transverse momentum, $p_{\mathrm{T}}^{J/\psi}$, in the range from 2 to 15 GeV/$c$. The results are in agreement with the next-to-leading order non-relativistic QCD model at high $p_{\mathrm{T}}^{J/\psi}$ and lie consistently above the pure leading-order colour singlet prediction.
Ratio of cross sections for $\chi_{c2}$ to $\chi_{c1}$ production in bins of $J/\psi$ transverse momentum over the $J/\psi$ rapidity range 2.0 to 4.5. The second systematic error represents the uncertainty in the $\chi_c \to J/\psi \gamma$ branching fractions with the maximum uncertainties from the unknown $\chi_c$ polarizations shown separately.
The production of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in proton-proton collisions at the centre-of-mass energy of sqrt(s)=7 TeV is studied with the LHCb detector. The analysis is based on a data sample of 25 pb-1 collected at the Large Hadron Collider. The Upsilon mesons are reconstructed in the decay mode Upsilon -> mu+ mu- and the signal yields are extracted from a fit to the mu+ mu- invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the Upsilon transverse momentum pT and rapidity y, over the range pT < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be sigma(pp -> Upsilon(1S) X) x B(Upsilon(1S)->mu+ mu-) = 2.29 {\pm} 0.01 {\pm} 0.10 -0.37 +0.19 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S)->mu+ mu-) = 0.562 {\pm} 0.007 {\pm} 0.023 -0.092 +0.048 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S)->mu+ mu-) = 0.283 {\pm} 0.005 {\pm} 0.012 -0.048 +0.025 nb, where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three Upsilon states.
Integrated cross-sections times dimuon branching fractions in the PT range < 15 GeV/c and rapidity in the range 2.0-4.0. The second systematic (sys) error is due to the unknown polarisation of the three states.
Double differential cross section for UPSI(1S) production times the dimuon branching fraction as a function of PT for the rapidity region 2.0-2.5. The second systematic (sys) error is due to the unknown polarisation of the UPSI(1S).
Double differential cross section for UPSI(1S) production times the dimuon branching fraction as a function of PT for the rapidity region 2.5-3.0. The second systematic (sys) error is due to the unknown polarisation of the UPSI(1S).
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