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Open Access Publications from the University of California

Scholarly Works (64 results)

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LBL Publications (2016)
Associated production of bottomonia and open charm hadrons in pp collisions at 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 combinations, Y(1S)D0, Y(2S)D0, Y(1S)D+, Y(2S)D+ and Y(1S)Ds+, is reported. Production crosssections are measured for Y(1S)D0 and Y(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.[Figure not available: see fulltext.]
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    LBL Publications (2018)
    The difference between the CP asymmetries in the decays Λc+ → pK−K+ and Λc+ → pπ−π+ is presented. Proton-proton collision data taken at centre-of-mass energies of 7 and 8 TeV collected by the LHCb detector in 2011 and 2012 are used, corresponding to an integrated luminosity of 3 fb−1. The Λc+ candidates are reconstructed as part of the Λb0 → Λc+μ−X decay chain. In order to maximize the cancellation of production and detection asymmetries in the difference, the final-state kinematic distributions of the two samples are aligned by applying phase-space-dependent weights to the Λc+ → pπ−π+ sample. This alters the definition of the integrated CP asymmetry to ACPwgt(pπ−π+). Both samples are corrected for reconstruction and selection efficiencies across the five-dimensional Λc+ decay phase space. The difference in CP asymmetries is found to be ΔACPwgt=ACP(pK−K+)−ACPwgt(pπ−π+)=(0.30±0.91±0.61)%, where the first uncertainty is statistical and the second is systematic.[Figure not available: see fulltext.].
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      LBL Publications (2016)
        • Article
        • Peer Reviewed
        LBL Publications (2014)
        The polarisation of prompt [Formula: see text] mesons is measured by performing an angular analysis of [Formula: see text] decays using proton-proton collision data, corresponding to an integrated luminosity of 1.0[Formula: see text], collected by the LHCb detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum [Formula: see text] and rapidity [Formula: see text] in the kinematic region [Formula: see text] and [Formula: see text], and is compared to theoretical models. No significant polarisation is observed.
          Cover page: Measurement of ψ (2<i>S</i>) polarisation in <i>pp</i> collisions at √<i>s</i>=7 TeV
          • Article
          • Peer Reviewed
          LBL Publications (2015)
          A search is performed for heavy long-lived charged particles using 3.0 [Formula: see text] of proton-proton collisions collected at [Formula: see text][Formula: see text] 7 and 8  TeV with the LHCb detector. The search is mainly based on the response of the ring imaging Cherenkov detectors to distinguish the heavy, slow-moving particles from muons. No evidence is found for the production of such long-lived states. The results are expressed as limits on the Drell-Yan production of pairs of long-lived particles, with both particles in the LHCb pseudorapidity acceptance, [Formula: see text]. The mass-dependent cross-section upper limits are in the range 2-4 fb (at 95 % CL) for masses between 14 and 309 [Formula: see text].
            Cover page: Search for long-lived heavy charged particles using a ring imaging Cherenkov technique at LHCb
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2014)
            A search for CP violation using T-odd correlations is performed using the four-body D0→ K+K-π+π−decay, selected from semileptonic B decays. The data sample corresponds to integrated luminosities of 1.0 fb-1and 2.0 fb-1recorded at the centre-of-mass energies of 7TeV and 8TeV, respectively. The CP-violating asymmetry (Formula presented.) is measured to be (0.18 ± 0.29 (stat) ± 0.04 (syst))%. Searches for CP violation in different regions of phase space of the four-body decay, and as a function of the D0decay time, are also presented. No significant deviation from the CP conservation hypothesis is found.
              Cover page: Search for CP violation using T-odd correlations in D0 → K+K−π+π− decaysCreative Commons 'BY' version 4.0 license
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              • Peer Reviewed
              UC Riverside Previously Published Works (2014)
              Measurements of the total and differential cross sections dσ/dp(T)(B) and dσ/dy(B) for B(+) mesons produced in pp collisions at sqrt[s]=7  TeV are presented. The data correspond to an integrated luminosity of 5.8  pb(-1) collected by the CMS experiment operating at the LHC. The exclusive decay B(+)→J/ψK(+), with J/ψ→μ(+)μ(-), is used to detect B(+) mesons and to measure the production cross section as a function of p(T)(B) and y(B). The total cross section for p(T)(B)>5  GeV and |y(B)|<2.4 is measured to be 28.1±2.4±2.0±3.1  μb, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement.
                Cover page: Measurement of the forward W boson cross-section in pp collisions at s=7 TeV
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                • Peer Reviewed
                UC Santa Cruz Previously Published Works (2016)
                We perform a search for near-threshold Ξb0 resonances decaying to Ξb−π+ in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. We observe one resonant state, with the following properties: (Formula presented.). This confirms the previous observation by the CMS collaboration. The state is consistent with the JP = 3/2+ Ξb∗0 resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratio (Formula presented.).
                  Creative Commons 'BY' version 4.0 license
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                  • Peer Reviewed
                  LBL Publications (2016)
                  Abstract: A search for B(s)0 → KS0K∗(892)0 decays is performed using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The Bs0 → KS0K∗(892)0 decay is observed for the first time, with a significance of 7.1 standard deviations. The branching fraction is measured to (formula presented.),at 90 % confidence level. All results are consistent with Standard Model predictions.[Figure not available: see fulltext.]
                    Cover page: First observation of the decay Bs0 → KS0K∗(892)0 at LHCb
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                    • Peer Reviewed
                    LBL Publications (2016)
                    A search is performed for the charmless three-body decays of the Λb0 and Ξb0 baryons to the final states Λh+h′−, where h(′) = π or K. The analysis is based on a data sample, corresponding to an integrated luminosity of 3 fb−1 of pp collisions, collected by the LHCb experiment. The Λb0 → ΛK+π− and Λb0 → ΛK+K− decays are observed for the first time and their branching fractions and CP asymmetry parameters are measured. Evidence is seen for the Λb0 → Λπ+π− decay and limits are set on the branching fractions of Ξb0 baryon decays to the Λh+h′− final states.
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