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Register a new userIdentification of beauty and charm quark jets at LHCb
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Identification of jets originating from beauty and charm quarks is important for measuring Standard Model processes and for searching for new physics. The performance of algorithms developed to select $b$- and $c$-quark jets is measured using data recorded by LHCb from proton-proton collisions at $sqrt{s}=7$ TeV in 2011 and at $sqrt{s}=8$ TeV in 2012. The efficiency for identifying a $b(c)$ jet is about 65%(25%) with a probability for misidentifying a light-parton jet of 0.3% for jets with transverse momentum $p_{rm T} > 20$ GeV and pseudorapidity $2.2 < eta < 4.2$. The dependence of the performance on the $p_{rm T}$ and $eta$ of the jet is also measured.
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The LHCb collaboration has recently performed a first measurement of the angular production asymmetry in the distribution of beauty quarks and anti-quarks at a hadron collider. We calculate the corresponding standard model prediction for this asymmetry at fixed-order in perturbation theory. Our results show good agreement with the data, which is provided differentially for three bins in the invariant mass of the $b bar b$ system. We also present similar predictions for both beauty-quark and charm-quark final states within the LHCb acceptance for a collision energy of $sqrt{s} = 13 , {rm TeV}$. We finally point out that a measurement of the ratio of the $b bar b$ and $c bar c$ cross sections may be useful for experimentally validating charm-tagging efficiencies.
Results on open charm and beauty production and on the search for top production in high-energy electron-proton collisions at HERA are reviewed. This includes a discussion of relevant theoretical aspects, a summary of the available measurements and measurement techniques, and their impact on improved understanding of QCD and its parameters, such as parton density functions and charm- and beauty-quark masses. The impact of these results on measurements at the LHC and elsewhere is also addressed.
The production of beauty and charm quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared 5 < Q^2 < 1000 GeV^2 using an integrated luminosity of 354 pb^{-1}. The beauty and charm content in events with at least one jet have been extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of Q^2, Bjorken x, jet transverse energy and pseudorapidity were measured and compared with next-to-leading-order QCD calculations. The beauty and charm contributions to the proton structure functions were extracted from the double-differential cross section as a function of x and Q^2. The running beauty-quark mass, m_b at the scale m_b, was determined from a QCD fit at next-to-leading order to HERA data for the first time and found to be 4.07 pm 0.14 (fit} ^{+0.01}_{-0.07} (mod.) ^{+0.05}_{-0.00} (param.) ^{+0.08}_{-0.05} (theo) GeV.
Selected new results from the H1 and ZEUS collaborations on $ep$ interactions at 300 - 318 GeV centre-of-mass energy are presented. The full pre-upgrade integrated luminosity of HERA of 110 pb$^{-1}$ is used. Charm cross sections are measured up to high values of $x_B$ and $Q^2$ and are found to be well described by NLO QCD in the 3 flavour scheme. Orbitally excited $D$ mesons are observed; radial excitations are searched for, but are not seen. The first $b$ cross section measurement is confirmed with a lifetime based method, establishing the excess over NLO QCD.
Recent charm spectroscopy results from Dalitz plot analyses of $B$ decays to open charm final states at LHCb are presented. The decay modes used are $B^{+} to D^{-} K^{+} pi^{+}$, $B^{0} to overline{D}{}^{0} pi^{+} pi^{-}$ and $B^{0} to overline{D}{}^{0} K^{+} pi^{-}$.
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