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Measurement of two-particle correlations with respect to second- and third-order event planes in Au + Au collisions at <math><mrow><msqrt><msub><mi>s</mi><mi>NN</mi></msub></msqrt><mo>=</mo><mn>200</mn></mrow></math> GeV
https://repo.scoap3.org/record/32638
We present measurements of azimuthal correlations of charged hadron pairs in sNN=200 GeV Au+Au collisions for the trigger and associated particle transverse-momentum ranges of 1<pTt<10GeV/c and 0.5<pTa<10GeV/c. After subtraction of an underlying event using a model that includes higher-order azimuthal anisotropy v2, v3, and v4, the away-side yield of the highest trigger-pT(pTt>4GeV/c) correlations is suppressed compared with that of correlations measured in p+p collisions. At the lowest associated particle pT(0.5<pTa<1GeV/c), the away-side shape and yield are modified relative to those in p+p collisions. These observations are consistent with the scenario of radiative-jet energy loss. For the low-pT trigger correlations (2<pTt<4GeV/c), a finite away-side yield exists and we explore the dependence of the shape of the away-side within the context of an underlying-event model. Correlations are also studied differentially versus event-plane angle Ψ2 and Ψ3. The angular correlations show an asymmetry when selecting the sign of the difference between the trigger-particle azimuthal angle and the Ψ2 event plane. This asymmetry and the measured suppression of the pair yield out-of-plane is consistent with a path-length-dependent energy loss. No Ψ3 dependence can be resolved within experimental uncertainties.Adare, A.Tue, 07 May 2019 20:16:59 GMThttps://repo.scoap3.org/record/32638urn:ISSN:2469-9993APS2019-05-07Nonperturbative-transverse-momentum broadening in dihadron angular correlations in <math><mrow><msqrt><msub><mi>s</mi><msub><mrow></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></msub></msqrt><mo>=</mo><mn>200</mn><mspace width="0.16em"></mspace><mi>GeV</mi></mrow></math> proton-nucleus collisions
https://repo.scoap3.org/record/32374
The PHENIX collaboration has measured high-pT dihadron correlations in p+p, p+Al, and p+Au collisions at sNN=200 GeV. The correlations arise from inter- and intrajet correlations and thus have sensitivity to nonperturbative effects in both the initial and final states. The distributions of pout, the transverse-momentum component of the associated hadron perpendicular to the trigger hadron, are sensitive to initial- and final-state transverse momenta. These distributions are measured multidifferentially as a function of xE, the longitudinal momentum fraction of the associated hadron with respect to the trigger hadron. The near-side pout widths, sensitive to fragmentation transverse momentum, show no significant broadening between p+Au, p+Al, and p+p. The away-side nonperturbative pout widths are found to be broadened in p+Au when compared to p+p; however, there is no significant broadening in p+Al compared to p+p collisions. The data also suggest that the away-side pout broadening is a function of Ncoll, the number of binary nucleon-nucleon collisions, in the interaction. The potential implications of these results with regard to initial- and final-state transverse-momentum broadening and energy loss of partons in a nucleus, among other nuclear effects, are discussed.Aidala, C.Thu, 18 Apr 2019 16:16:42 GMThttps://repo.scoap3.org/record/32374urn:ISSN:2469-9993APS2019-04-18Model-Independent Observation of Exotic Contributions to <math><msup><mi>B</mi><mn>0</mn></msup><mo>→</mo><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow><msup><mi>K</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> Decays
https://repo.scoap3.org/record/32365
An angular analysis of B0→J/ψK+π− decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected with the LHCb detector. The m(K+π−) spectrum is divided into fine bins. In each m(K+π−) bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by K* resonances is examined, making minimal assumptions about the K+π− system. The data reject the K*-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the m(J/ψπ−) vs m(K+π−) plane suggests structures near m(J/ψπ−)=4200 and 4600 MeV.Aaij, R.Thu, 18 Apr 2019 04:16:44 GMThttps://repo.scoap3.org/record/32365urn:ISSN:1079-7114APS2019-04-17Measurements of <math><mi>μ</mi><mi>μ</mi></math> pairs from open heavy flavor and Drell-Yan in <math><mi>p</mi><mo>+</mo><mi>p</mi></math> collisions at <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>
https://repo.scoap3.org/record/32201
PHENIX reports differential cross sections of μμ pairs from semileptonic heavy-flavor decays and the Drell-Yan production mechanism measured in p+p collisions at s=200 GeV at forward and backward rapidity (1.2<|η|<2.2). The μμ pairs from cc¯, bb¯, and Drell-Yan are separated using a template fit to unlike- and like-sign muon pair spectra in mass and pT. The azimuthal opening angle correlation between the muons from cc¯ and bb¯ decays and the pair-pT distributions are compared to distributions generated using pythia and powheg models, which both include next-to-leading order processes. The measured distributions for pairs from cc¯ are consistent with pythia calculations. The cc¯ data present narrower azimuthal correlations and softer pT distributions compared to distributions generated from powheg. The bb¯ data are well described by both models. The extrapolated total cross section for bottom production is 3.75±0.24(stat)±0.500.35(syst)±0.45(global) [μb], which is consistent with previous measurements at the Relativistic Heavy Ion Collider in the same system at the same collision energy and is approximately a factor of 2 higher than the central value calculated with theoretical models. The measured Drell-Yan cross section is in good agreement with next-to-leading-order quantum-chromodynamics calculations.Aidala, C.Wed, 10 Apr 2019 20:16:11 GMThttps://repo.scoap3.org/record/32201urn:ISSN:2470-0029APS2019-04-10First Measurement of Charm Production in its Fixed-Target Configuration at the LHC
https://repo.scoap3.org/record/32041
The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/ψ and D0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of sNN=86.6 and 110.4 GeV, respectively. The J/ψ and D0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be σJ/ψ=652±33(stat)±42(syst) nb/nucleon and σD0=80.8±2.4(stat)±6.3(syst) μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region.Aaij, R.Tue, 09 Apr 2019 15:06:37 GMThttps://repo.scoap3.org/record/32041urn:ISSN:1079-7114APS2019-04-02Measurement of <math><msup><mi>B</mi><mo>+</mo></msup></math>, <math><msup><mi>B</mi><mn>0</mn></msup></math> and <math><msubsup><mi>Λ</mi><mi>b</mi><mn>0</mn></msubsup></math> production in <math><mrow><mi>p</mi><mi>Pb</mi></mrow></math> collisions at <math><msqrt><msub><mi>s</mi><mrow><mi>NN</mi></mrow></msub></msqrt><mo>=</mo><mn>8.16</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>
https://repo.scoap3.org/record/31887
The production of B+, B0 and Λb0 hadrons is studied in proton-lead collisions at a center-of-mass energy per nucleon pair of sNN=8.16 TeV recorded with the LHCb detector at the LHC. The measurement uses a dataset corresponding to an integrated luminosity of 12.2±0.3 nb−1 for the case where the proton beam is projected into the LHCb detector (corresponding to measuring hadron production at positive rapidity) and 18.6±0.5 nb−1 for the lead beam projected into the LHCb detector (corresponding to measuring hadron production at negative rapidity). Double-differential cross sections are measured and used to determine forward-backward ratios and nuclear modification factors, which directly probe nuclear effects in the production of beauty hadrons. The double-differential cross sections are measured as a function of the beauty-hadron transverse momentum and rapidity in the nucleon-nucleon center-of-mass frame. Forward-to-backward cross section ratios and nuclear modification factors indicate a significant nuclear suppression at positive rapidity. The ratio of Λb0 over B0 production cross sections is reported and is consistent with the corresponding measurement in pp collisions.Aaij, R.Wed, 27 Mar 2019 21:17:25 GMThttps://repo.scoap3.org/record/31887urn:ISSN:2470-0029APS2019-03-27Measurement of the mass and production rate of <math><msubsup><mi>Ξ</mi><mi>b</mi><mo>−</mo></msubsup></math> baryons
https://repo.scoap3.org/record/31714
The first measurement of the production rate of Ξb− baryons in pp collisions relative to that of Λb0 baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of 1, 2 and 1.6 fb−1 at s=7, 8 and 13 TeV, respectively. In the kinematic region 2<η<6 and pT<20 GeV/c, we measure fΞb−fΛb0B(Ξb−→J/ψΞ−)B(Λb0→J/ψΛ)=(10.8±0.9±0.8)×10−2 [s=7,8 TeV], fΞb−fΛb0B(Ξb−→J/ψΞ−)B(Λb0→J/ψΛ)=(13.1±1.1±1.0)×10−2 [s=13 TeV], where fΞb− and fΛb0 are the fragmentation fractions of b quarks into Ξb− and Λb0 baryons, respectively; B represents branching fractions; and the uncertainties are due to statistical and experimental systematic sources. The values of fΞb−/fΛb0 are obtained by invoking SU(3) symmetry in the Ξb−→J/ψΞ− and Λb0→J/ψΛ decays. Production asymmetries between Ξb− and Ξ¯b+ baryons are also reported. The mass of the Ξb− baryon is also measured relative to that of the Λb0 baryon, from which it is found that m(Ξb−)=5796.70±0.39±0.15±0.17 MeV/c2, where the last uncertainty is due to the precision on the known Λb0 mass. This result represents the most precise determination of the Ξb− mass.Aaij, R.Sat, 23 Mar 2019 01:16:07 GMThttps://repo.scoap3.org/record/31714urn:ISSN:2470-0029APS2019-03-22Observation of Two Resonances in the <math><msubsup><mi>Λ</mi><mi>b</mi><mn>0</mn></msubsup><msup><mi>π</mi><mo>±</mo></msup></math> Systems and Precise Measurement of <math><msubsup><mi>Σ</mi><mi>b</mi><mo>±</mo></msubsup></math> and <math><msubsup><mi>Σ</mi><mi>b</mi><mrow><mo>*</mo><mo>±</mo></mrow></msubsup></math> Properties
https://repo.scoap3.org/record/30225
The first observation of two structures consistent with resonances in the final states Λb0π− and Λb0π+ is reported using samples of pp collision data collected by the LHCb experiment at s=7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. The ground states Σb± and Σb*± are also confirmed and their masses and widths are precisely measured.Aaij, R.Fri, 11 Jan 2019 15:17:58 GMThttps://repo.scoap3.org/record/30225urn:ISSN:1079-7114APS2019-01-11Measurement of the Charm-Mixing Parameter <math><msub><mi>y</mi><mrow><mi>C</mi><mi>P</mi></mrow></msub></math>
https://repo.scoap3.org/record/30222
A measurement of the charm-mixing parameter yCP using D0→K+K−, D0→π+π−, and D0→K−π+ decays is reported. The D0 mesons are required to originate from semimuonic decays of B− and B¯0 mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb−1. The yCP parameter is measured to be (0.57±0.13(stat)±0.09(syst))%, in agreement with, and as precise as, the current world-average value.Aaij, R.Fri, 11 Jan 2019 15:17:46 GMThttps://repo.scoap3.org/record/30222urn:ISSN:1079-7114APS2019-01-08Evidence for an ηc(1S)π- resonance in B0→ηc(1S)K+π- decays
https://repo.scoap3.org/record/29859
A Dalitz plot analysis of B0→ηc(1S)K+π- decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of s=7,8 and 13TeV , corresponding to a total integrated luminosity of 4.7fb-1 . A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1S)π- resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096±20-22+18MeV and 152±58-35+60MeV , respectively. The spin-parity assignments JP=0+ and JP=1- are both consistent with the data. In addition, the first measurement of the B0→ηc(1S)K+π- branching fraction is performed and gives B(B0→ηc(1S)K+π-)=(5.73±0.24±0.13±0.66)×10-4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions.Aaij, R.Mon, 17 Dec 2018 13:33:25 GMThttps://repo.scoap3.org/record/29859urn:ISSN:1434-6052Springer/Società Italiana di Fisica2018-12-17Search for lepton-flavour-violating decays of Higgs-like bosons
https://repo.scoap3.org/record/29701
A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/c2 decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV , collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1 . The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/c2 to 4 pb for a mass of 195 GeV/c2 .Aaij, R.Thu, 13 Dec 2018 14:44:42 GMThttps://repo.scoap3.org/record/29701urn:ISSN:1434-6052Springer/Società Italiana di Fisica2018-12-12Measurement of Antiproton Production in <math><mrow><mi>p</mi><mtext>−</mtext><mi>He</mi></mrow></math> Collisions at <math><mrow><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>NN</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>110</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>
https://repo.scoap3.org/record/29588
The cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of 0.5 nb−1. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV/c, represent the first direct determination of the antiproton production cross section in p−He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.Aaij, R.Mon, 03 Dec 2018 17:19:30 GMThttps://repo.scoap3.org/record/29588urn:ISSN:1079-7114APS2018-11-29Production of <math><msup><mi>π</mi><mn>0</mn></msup></math> and <math><mi>η</mi></math> mesons in <math><mrow><mi>Cu</mi><mo>+</mo><mi>Au</mi></mrow></math> collisions at <math><mrow><msqrt><msub><mi>s</mi><msub><mrow></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></msub></msqrt><mo>=</mo><mn>200</mn><mspace width="0.28em"></mspace><mi>GeV</mi></mrow></math>
https://repo.scoap3.org/record/29302
Production of π0 and η mesons has been measured at midrapidity in Cu+Au collisions at sNN=200GeV. Measurements were performed in π0(η)→γγ decay channel in the 1(2)−20GeV/c transverse momentum range. A strong suppression is observed for π0 and η meson production at high transverse momentum in central Cu+Au collisions relative to the p+p results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au+Au with comparable nuclear overlap. The η/π0 ratio measured as a function of transverse momentum is consistent with mT-scaling parametrization down to pT=2GeV/c, its asymptotic value is constant and consistent with Au+Au and p+p and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in e+e− collisions in a range of collision energies sNN=3−1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu+Cu collisions either does not affect the jet fragmentation into light mesons or it affects the π0 and η the same way.Aidala, C.Mon, 19 Nov 2018 17:16:51 GMThttps://repo.scoap3.org/record/29302urn:ISSN:2469-9993APS2018-11-19Low-momentum direct-photon measurement in Cu + Cu collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>200</mn><mspace width="4pt"></mspace><mi>GeV</mi></mrow></math>
https://repo.scoap3.org/record/29208
We measured direct photons for pT<5GeV/c in minimum bias and 0%–40% most-central events at midrapidity for Cu+Cu collisions at sNN=200GeV. The e+e− contribution from quasireal direct virtual photons has been determined as an excess over the known hadronic contributions in the e+e− mass distribution. A clear enhancement of photons over the binary scaled p+p fit is observed for pT<4GeV/c in Cu+Cu data. The pT spectra are consistent with the Au+Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the p+p baseline are 285±53(stat)±57(syst)MeV/c and 333±72(stat)±45(syst)MeV/c for minimum bias and 0%–40% most-central events, respectively. The rapidity density, dN/dy, of photons demonstrates the same power law as a function of dNch/dη observed in Au+Au at the same collision energy.Adare, A.Thu, 15 Nov 2018 17:16:06 GMThttps://repo.scoap3.org/record/29208urn:ISSN:2469-9993APS2018-11-15Measurement of <math><mi>ϕ</mi></math>-meson production at forward rapidity in <math><mi>p</mi><mo>+</mo><mi>p</mi></math> collisions at <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>510</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and its energy dependence from <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> to 7 TeV
https://repo.scoap3.org/record/29096
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of ϕ(1020)-meson production at forward rapidity in p+p collisions at s=510 GeV via the dimuon decay channel. The partial cross section in the rapidity and pT ranges 1.2<|y|<2.2 and 2<pT<7 GeV/c is σϕ=[2.28±0.09(stat)±0.14(syst)±0.27(norm)]×10−2 mb. The energy dependence of σϕ (1.2<|y|<2.2,2<pT<5 GeV/c) is studied using the PHENIX measurements at s=200 and 510 GeV and the Large Hadron Collider measurements at s=2.76 and 7 TeV. The experimental results are compared to various event generator predictions (pythia6, pythia8, phojet, ampt, epos3, and epos-lhc).Adare, A.Fri, 09 Nov 2018 17:16:34 GMThttps://repo.scoap3.org/record/29096urn:ISSN:2470-0029APS2018-11-09Observation of the decay <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo>→</mo><msup><mrow><mover><mrow><mi>D</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math>
https://repo.scoap3.org/record/29003
The first observation of the Bs0→D¯0K+K− decay is reported, together with the most precise branching fraction measurement of the mode B0→D¯0K+K−. The results are obtained from an analysis of pp collision data corresponding to an integrated luminosity of 3.0 fb−1. The data were collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction of the B0→D¯0K+K− decay is measured relative to that of the decay B0→D¯0π+π− to be B(B0→D¯0K+K−)B(B0→D¯0π+π−)=(6.9±0.4±0.3)%, where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the Bs0→D¯0K+K− decay mode relative to that of the corresponding B0 decay is B(Bs0→D¯0K+K−)B(B0→D¯0K+K−)=(93.0±8.9±6.9)%. Using the known branching fraction of B0→D¯0π+π−, the values of B(B0→D¯0K+K−)=(6.1±0.4±0.3±0.3)×10−5 and B(Bs0→D¯0K+K−)=(5.7±0.5±0.4±0.5)×10−5 are obtained, where the third uncertainties arise from the branching fraction of the decay modes B0→D¯0π+π− and B0→D¯0K+K−, respectively.Aaij, R.Tue, 06 Nov 2018 13:18:41 GMThttps://repo.scoap3.org/record/29003urn:ISSN:2470-0029APS2018-10-31Observation of <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo>→</mo><msup><mrow><mover><mrow><mi>D</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mo>*</mo><mn>0</mn></mrow></msup><mi>ϕ</mi></mrow></math> and search for <math><msup><mi>B</mi><mn>0</mn></msup><mo>→</mo><msup><mover><mi>D</mi><mo>¯</mo></mover><mn>0</mn></msup><mi>ϕ</mi></math> decays
https://repo.scoap3.org/record/28896
The first observation of the Bs0→D¯*0ϕ decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3 fb−1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay B0→D¯0π+π− and is found to be B(Bs0→D¯*0ϕ)=(3.7±0.5±0.3±0.2)×10−5, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the B0→D¯0π+π− decay. The fraction of longitudinal polarization in this decay is measured to be fL=(73±15±4)%. The most precise determination of the branching fraction for the Bs0→D¯0ϕ decay is also obtained, B(Bs0→D¯0ϕ)=(3.0±0.3±0.2±0.2)×10−5. An upper limit, B(B0→D¯0ϕ)<2.0 (2.3)×10−6 at 90% (95%) confidence level is set. A constraint on the ω−ϕ mixing angle δ is set at |δ|<5.2° (5.5°) at 90% (95%) confidence level.Aaij, R.Tue, 30 Oct 2018 21:16:10 GMThttps://repo.scoap3.org/record/28896urn:ISSN:2470-0029APS2018-10-30Search for CP violation in Λb0→pK− and Λb0→pπ− decays
https://repo.scoap3.org/record/28754
A search for CP violation in Λb0→pK− and Λb0→pπ− decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0 fb−1 . The CP -violating asymmetries are measured to be ACPpK−=−0.020±0.013±0.019 and ACPpπ−=−0.035±0.017±0.020 , and their difference ACPpK−−ACPpπ−=0.014±0.022±0.010 , where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date.Aaij, R.Wed, 24 Oct 2018 16:08:29 GMThttps://repo.scoap3.org/record/28754urn:ISSN:0370-2693Elsevier2018-12-10First Observation of the Doubly Charmed Baryon Decay <math><msubsup><mi>Ξ</mi><mrow><mi>c</mi><mi>c</mi></mrow><mrow><mo>+</mo><mo>+</mo></mrow></msubsup><mo>→</mo><msubsup><mi>Ξ</mi><mi>c</mi><mo>+</mo></msubsup><msup><mi>π</mi><mo>+</mo></msup></math>
https://repo.scoap3.org/record/28665
The doubly charmed baryon decay Ξcc++→Ξc+π+ is observed for the first time, with a statistical significance of 5.9σ, confirming a recent observation of the baryon in the Λc+K−π+π+ final state. The data sample used corresponds to an integrated luminosity of 1.7 fb−1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 13 TeV. The Ξcc++ mass is measured to be 3620.6±1.5(stat)±0.4(syst)±0.3(Ξc+) MeV/c2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be [B(Ξcc++→Ξc+π+)×B(Ξc+→pK−π+)]/[B(Ξcc++→Λc+K−π+π+)×B(Λc+→pK−π+)]=0.035±0.009(stat)±0.003(syst).Aaij, R.Thu, 18 Oct 2018 00:16:19 GMThttps://repo.scoap3.org/record/28665urn:ISSN:1079-7114APS2018-10-17Nonperturbative transverse-momentum-dependent effects in dihadron and direct photon-hadron angular correlations in <math><mi>p</mi><mo>+</mo><mi>p</mi></math> collisions at <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>
https://repo.scoap3.org/record/28652
Dihadron and isolated direct photon-hadron angular correlations are measured in p+p collisions at s=200 GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momenta kT and jT in the azimuthal nearly back-to-back region Δϕ∼π. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of pout, the out-of-plane transverse-momentum component perpendicular to the trigger particle, are measured. In this region, the evolution of pout can be studied when several different hard scales are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal-momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions, where factorization is predicted to hold. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at s=510 GeV. The nonperturbative jet widths also appear to increase with s at a similar xT, which is qualitatively consistent to similar measurements in Drell-Yan interactions. Future detailed global comparisons between measurements of processes where transverse-momentum-dependent factorization is predicted to hold and be broken will provide further insight into the role of color in hadronic interactions.Aidala, C.Wed, 17 Oct 2018 16:16:06 GMThttps://repo.scoap3.org/record/28652urn:ISSN:2470-0029APS2018-10-17Measurement of the <math><msubsup><mi>Ω</mi><mi>c</mi><mn>0</mn></msubsup></math> Baryon Lifetime
https://repo.scoap3.org/record/27754
We report a measurement of the lifetime of the Ωc0 baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment. The sample consists of about 1000 Ωb−→Ωc0μ−ν¯μX signal decays, where the Ωc0 baryon is detected in the pK−K−π+ final state and X represents possible additional undetected particles in the decay. The Ωc0 lifetime is measured to be τΩc0=268±24±10±2 fs, where the uncertainties are statistical, systematic, and from the uncertainty in the D+ lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value.Aaij, R.Fri, 31 Aug 2018 16:17:06 GMThttps://repo.scoap3.org/record/27754urn:ISSN:1079-7114APS2018-08-31Measurement of Angular and <math><mi>C</mi><mi>P</mi></math> Asymmetries in <math><msup><mi>D</mi><mn>0</mn></msup><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> and <math><msup><mi>D</mi><mn>0</mn></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> Decays
https://repo.scoap3.org/record/27730
The first measurements of the forward-backward asymmetry of the dimuon pair (AFB), the triple-product asymmetry (A2ϕ), and the charge-parity-conjugation asymmetry (ACP), in D0→π+π−μ+μ− and D0→K+K−μ+μ− decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5 fb−1. The asymmetries are measured to be AFB(D0→π+π−μ+μ−)=(3.3±3.7±0.6)%, A2ϕ(D0→π+π−μ+μ−)=(−0.6±3.7±0.6)%, ACP(D0→π+π−μ+μ−)=(4.9±3.8±0.7)%, AFB(D0→K+K−μ+μ−)=(0±11±2)%, A2ϕ(D0→K+K−μ+μ−)=(9±11±1)%, ACP(D0→K+K−μ+μ−)=(0±11±2)%, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions.Aaij, R.Thu, 30 Aug 2018 20:16:52 GMThttps://repo.scoap3.org/record/27730urn:ISSN:1079-7114APS2018-08-30Observation of a New <math><mrow><msubsup><mrow><mi>Ξ</mi></mrow><mrow><mi>b</mi></mrow><mrow><mo>−</mo></mrow></msubsup></mrow></math> Resonance
https://repo.scoap3.org/record/27395
From samples of pp collision data collected by the LHCb experiment at s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb−1, respectively, a peak in both the Λb0K− and Ξb0π− invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξb− resonances with quark content bds are expected. Referring to this peak as Ξb(6227)−, the mass and natural width are measured to be mΞb(6227)−=6226.9±2.0±0.3±0.2 MeV/c2 and ΓΞb(6227)−=18.1±5.4±1.8 MeV/c2, where the first uncertainty is statistical, the second is systematic, and the third, on mΞb(6227)−, is due to the knowledge of the Λb0 baryon mass. Relative production rates of the Ξb(6227)−→Λb0K− and Ξb(6227)−→Ξb0π− decays are also reported.Aaij, R.Thu, 16 Aug 2018 00:16:51 GMThttps://repo.scoap3.org/record/27395urn:ISSN:1079-7114APS2018-08-15Cross section and longitudinal single-spin asymmetry <math><msub><mi>A</mi><mi>L</mi></msub></math> for forward <math><msup><mi>W</mi><mo>±</mo></msup><mo>→</mo><msup><mi>μ</mi><mo>±</mo></msup><mi>ν</mi></math> production in polarized <math><mi>p</mi><mo>+</mo><mi>p</mi></math> collisions at <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>510</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>
https://repo.scoap3.org/record/27369
We have measured the cross section and single-spin asymmetries from forward W±→μ±ν production in longitudinally polarized p+p collisions at s=510 GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the W bosons provides a natural flavor separation of the participating partons.Adare, A.Tue, 14 Aug 2018 20:16:10 GMThttps://repo.scoap3.org/record/27369urn:ISSN:2470-0029APS2018-08-14Measurement of <math><mi>C</mi><mi>P</mi></math> asymmetries in two-body <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow><mrow><mn>0</mn></mrow></msubsup></mrow></math>-meson decays to charged pions and kaons
https://repo.scoap3.org/record/27330
The time-dependent CP asymmetries in B0→π+π− and Bs0→K+K− decays are measured using a data sample of p p collisions corresponding to an integrated luminosity of 3.0 fb−1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated CP asymmetries in B0→K+π− and Bs0→π+K− decays. The results are Cπ+π−=−0.34±0.06±0.01, Sπ+π−=−0.63±0.05±0.01, CK+K−=0.20±0.06±0.02, SK+K−=0.18±0.06±0.02, AK+K−ΔΓ=−0.79±0.07±0.10, ACPB0=−0.084±0.004±0.003, and ACPBs0=0.213±0.015±0.007, where the first uncertainties are statistical and the second systematic. Evidence for CP violation is found in the Bs0→K+K− decay for the first time.Aaij, R.Tue, 14 Aug 2018 12:36:58 GMThttps://repo.scoap3.org/record/27330urn:ISSN:2470-0029APS2018-08-10