اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMeasurement of the $chi_b(3P)$ mass and of the relative rate of $chi_{b1}(1P)$ and $chi_{b2}(1P)$ production
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The production of $chi_b$ mesons in proton-proton collisions is studied using a data sample collected by the LHCb detector, at centre-of-mass energies of $sqrt{s}=7$ and $8$ TeV and corresponding to an integrated luminosity of 3.0 fb$^{-1}$. The $chi_b$ mesons are identified through their decays to $Upsilon(1S)gamma$ and $Upsilon(2S)gamma$ using photons that converted to $e^+e^-$ pairs in the detector. The relative prompt production rate of $chi_{b1}(1P)$ and $chi_{b2}(1P)$ mesons is measured as a function of the $Upsilon(1S)$ transverse momentum in the $chi_b$ rapidity range $2.0<y<4.5$. A precise measurement of the $chi_b(3P)$ mass is also performed. Assuming a mass splitting between the $chi_{b1}(3P)$ and the $chi_{b2}(3P)$ states of 10.5 MeV/$c^2$, the measured mass of the $chi_{b1}(3P)$ meson is $ m(chi_{b1}(3P))= 10515.7^{+2.2}_{-3.9}(stat) ^{+1.5}_{-2.1}(syst) MeV/c^2.$
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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 $J/psigamma$, w
ith $J/psitomu^+mu^-$ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of $1.0mathrm{fb}^{-1}$ collected by the LHCb detector, is used to measure the relative prompt production rate of $chi_{c1}$ and $chi_{c2}$ in the rapidity range $2.0<y<4.5$ as a function of the $J/psi$ transverse momentum from 3 to 20 GeV$/c$. First evidence for $chi_{c0}$ meson production at a high-energy hadron collider is also presented.
In this paper, the dilepton electromagnetic decays $chi_{cJ}(1P) to J/psi e^+e^-$ and $chi_{cJ}(1P) to Jpsi mu^+mu^-$, where $chi_{cJ}$ denotes $chi_{c0}$, $chi_{c1}$ and $chi_{c2}$, are calculated systematically in the improved Bethe-Salpeter method
. The numerical results of decay widths and the invariant mass distributions of the final lepton pairs are given. The comparison is made with the recently measured experimental data of BESIII. It is shown that for the cases including $e^+e^-$, the gauge invariance is decisive and should be considered carefully. For the processes of $chi_{cJ}(1P) to J/psi e^+e^-$, the branching fraction are: $mathcal{B}[chi_{c0}(1P) to J/psi e^+e^-]=1.06^{+0.16}_{-0.18} times 10^{-4}$, $mathcal{B}[chi_{c1}(1P) to J/psi e^+e^-]=2.88^{+0.50}_{-0.53} times 10^{-3}$, and $mathcal{B}[chi_{c2}(1P) to J/psi e^+e^-]=1.74^{+0.22}_{-0.21} times 10^{-3}$. The calculated branching fractions of $chi_{cJ}(1P)to J/psi mu^+mu^-$ channels are: $mathcal{B}[chi_{c0}(1P) to J/psi mu^+mu^-]=3.80^{+0.59}_{-0.64} times 10^{-6}$, $mathcal{B}[chi_{c1}(1P) to J/psi mu^+mu^-]=2.04^{+0.36}_{-0.38} times 10^{-4}$, and $mathcal{B}[chi_{c2}(1P) to J/psi mu^+mu^-]=1.66^{+0.19}_{-0.19} times 10^{-4}$.
Using a total of $9.0~mathrm{fb}^{-1}$ of $e^+e^-$ collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes $e^+e^-to gamma X(3872)$ with $X(3872)topi^0chi_{cJ}$ for $J=0,1,2$
. We report the first observation of $X(3872)topi^{0}chi_{c1}$, a new decay mode of the $X(3872)$, with a statistical significance of more than 5$sigma$. Normalizing to the previously established process $e^+e^-to gamma X(3872)$ with $X(3872)topi^+pi^-J/psi$, we find ${cal B}(X(3872) to pi^0 chi_{c1})/{cal B}(X(3872) to pi^+pi^- J/psi) = 0.88^{+0.33}_{-0.27}pm0.10$, where the first error is statistical and the second is systematic. We set 90% confidence level upper limits on the corresponding ratios for the decays to $pi^0chi_{c0}$ and $pi^0chi_{c2}$ of 19 and 1.1, respectively.
We report a study of radiative decays of chi_{bJ}(1P)(J=0,1,2) mesons into 74 hadronic final states comprising charged and neutral pions, kaons, protons; out of these, 41 modes are observed with at least 5 standard deviation significance. Our measure
ments not only improve the previous measurements by the CLEO Collaboration but also lead to first observations in many new modes. The large sample allows us to probe the total decay width of the chi_{b0}(1P). In the absence of a statistically significant result, a 90% confidence-level upper limit is set on the width at Gamma_{total}< 2.4 MeV. Our results are based on 24.7 fb^{-1} of e+e- collision data recorded by the Belle detector at the Upsilon(2S) resonance, corresponding to (157.8pm3.6)times10^6 Upsilon(2S) decays.
Using 9.32, 5.88 million Upsilon(2S,3S) decays taken with the CLEO-III detector, we obtain five product branching fractions for the exclusive processes Upsilon(2S) => gamma chi_{b0,1,2}(1P) => gamma gamma Upsilon(1S) and Upsilon(3S) => gamma chi_{b1,
2}(1P) => gamma gamma Upsilon(1S). We observe the transition chi_{b0}(1P) => gamma Upsilon(1S) for the first time. Using the known branching fractions for B[Upsilon(2S) => gamma chi_{bJ}(1P)], we extract values for B[chi_{bJ}(1P) => gamma Upsilon(1S)] for J=0, 1, 2. In turn, these values can be used to unfold the Upsilon(3S) product branching fractions to obtain values for B[Upsilon(3S) => gamma chi_{b1,2}(1P) for the first time individually. Comparison of these with each other and with the branching fraction B[Upsilon(3S) => gamma chi_{b0}] previously measured by CLEO provides tests of relativistic corrections to electric dipole matrix elements.
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