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1.
  • Ablikim, M., et al. (författare)
  • Observation of the Semileptonic Decay D-0 -> a(0)(980)(-)e(+)nu(e) and Evidence for D+ -> a(0)(980)(0)e(+)nu(e)
  • 2018
  • Ingår i: Physical Review Letters. - AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:8
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Using an e(+)e(-) collision data sample of 2.93 fb(-1) collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D-0 -&gt; a(0)(980)(-)e(+)nu(e) and evidence for D+ -&gt; a(0)(980)(0)e(+)nu(e) with significances of 6.4 sigma and 2.9 sigma, respectively. The absolute branching fractions are determined to be B(D-0 -&gt; a(0)(980)(-)e(+)nu(e)) x B(a(0)(980)(-) -&gt; eta pi(-)) = [1.33(-0.29)(+0.33)(stat) +/- 0.09(syst)] x 10(-4) and B(D+ -&gt; a(0)(980)(0)e(+)nu(e)) x B(a(0)(980)(0) -&gt; eta pi(0)) = [1.66(-0.66)(+0.81)(stat) +/- 0.11(syst) x 10(-4). This is the first time the a(0)(980) meson has been measured in a D-0 semileptonic decay, which would open one more interesting page in the investigation of the nature of the puzzling a(0)(980) states.</p>
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2.
  • Ablikim, M., et al. (författare)
  • Search for the rare decays D -&gt; h(h((')))e(+) e(-)
  • 2018
  • Ingår i: Physical Review D : covering particles, fields, gravitation, and cosmology. - AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:7
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We search for rare decays of D mesons to hadrons accompanied by an electron-positron pair (h(h((')))e(+)e(- )),using an e(+)e(-) collision sample corresponding to an integrated luminosity of 2.93 fb(-1) collected with the BESIII detector at root s = 3.773 GeV. No significant signals are observed, and the corresponding upper limits on the branching fractions at the 90% confidence level are determined. The sensitivities of the results are at the level of 10(-5)-10(-6), providing a large improvement over previous searches.</p>
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3.
  • Adare, A., et al. (författare)
  • Low-mass vector-meson production at forward rapidity in p plus p collisions at root s=200 GeV
  • 2014
  • Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - American Physical Society. - 1550-2368. ; 90:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low-mass vector-meson ,omega, rho, and phi, production through the dimuon decay channel at forward rapidity (1.2 < vertical bar y vertical bar < 2.2) in p + p collisions at root s = 200 GeV. The differential cross sections for these mesons are measured as a function of both p(T) and rapidity. We also report the integrated differential cross sections over 1 < p(T) < 7 GeV/c and 1.2 < vertical bar y vertical bar < 2.2: d sigma/dy(omega + rho rho -> mu mu) = 80 +/- 6(stat) +/- 12(syst)nb and d sigma/dy(phi -> mu mu) = 27 +/- 3(stat) +/- 4(syst)nb. These results are compared with midrapidity measurements and calculations.
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4.
  • Ablikim, M., et al. (författare)
  • Search for invisible decays of omega and phi with J/psi data at BESIII
  • 2018
  • Ingår i: Physical Review D : covering particles, fields, gravitation, and cosmology. - American Physical Society. - 2470-0010 .- 2470-0029. ; 98:3
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Using a data sample of (1310.6 +/- 7.0) x 10(6) J/psi events collected with the BESIII detector operating at the BEPCII collider, we perform the first experimental search for invisible decays of a light vector meson (V = omega, phi) via J/psi -&gt; V-eta decays. The decay of eta -&gt; pi(+)pi(-)pi(0) is utilized to tag the V meson decaying into the invisible final state. No evidence for a significant invisible signal is observed, and the upper limits on the ratio of branching fractions at the 90% confidence level are determined to be B(omega -&gt; invisible)/B(omega -&gt; pi(+)pi(-)pi(0)) &lt; 8.1 x 10(-5) and B(phi -&gt; invisible)/B(phi -&gt; K+K-) &lt; 3.4 x 10(-4). By using the world average values of B(omega -&gt; pi(+)pi(-)pi(0) and B(phi -&gt; K+K-,) the upper limits on the decay branching fractions at the 90% confidence level are set as B(omega -&gt; invisible) &lt; 7.3 x 10(-5) and B(phi -&gt; invisible) &lt; 1.7 x 10(-4), respectively.</p>
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5.
  • Adare, A., et al. (författare)
  • Cold nuclear matter effects on J/psi production as constrained by deuteron-gold measurements at root S-NN=200 GeV
  • 2008
  • Ingår i: Physical Review C (Nuclear Physics). - American Physical Society. - 0556-2813. ; 77:2, s. 15-024912
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a new analysis of J/psi production yields in deuteron-gold collisions at root s(NN) =200 GeV using data taken from the PHENIX experiment in 2003 and previously published in S. S. Adler [Phys. Rev. Lett 96, 012304 (2006)]. The high statistics proton-proton J/psi data taken in 2005 are used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors (R-dAu). A suppression of J/psi in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial-state low-x gluons in the gold nucleus. The measured nuclear modification factors are compared to theoretical calculations of nuclear shadowing to which a J/psi (or precursor) breakup cross section is added. Breakup cross sections of sigma(breakup)=2.8(-1.4)(+1.7) (2.2(-1.5)(+1.6)) mb are obtained by fitting these calculations to the data using two different models of nuclear shadowing. These breakup cross-section values are consistent within large uncertainties with the 4.2 +/- 0.5 mb determined at lower collision energies. Projecting this range of cold nuclear matter effects to copper-copper and gold-gold collisions reveals that the current constraints are not sufficient to firmly quantify the additional hot nuclear matter effect.
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6.
  • Adare, A., et al. (författare)
  • Cross section and transverse single-spin asymmetry of eta mesons in p up arrow plus p collisions at root s=200 GeV at forward rapidity
  • 2014
  • Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - American Physical Society. - 1550-2368. ; 90:7
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of the cross section and transverse single-spin asymmetry (AN) for. mesons at large pseudorapidity from root s = 200 GeV p up arrow + p collisions. The measured cross section for 0.5 < p(T) < 5.0 GeV/c and 3.0 < vertical bar eta vertical bar < 3.8 is well described by a next-to-leading-order perturbative-quantum-chromodynamics calculation. The asymmetries A(N) have been measured as a function of Feynman-x (x(F)) from 0.2 < vertical bar x(F)vertical bar < 0.7, as well as transverse momentum (p(T)) from 1.0 < p(T) < 4.5 GeV/c. The asymmetry averaged over positive x(F) is < A(N)> = 0.061 +/- 0.014. The results are consistent with prior transverse single-spin measurements of forward eta and pi(0) mesons at various energies in overlapping x(F) ranges. Comparison of different particle species can help to determine the origin of the large observed asymmetries in p up arrow + p collisions.
7.
  • Ablikim, M., et al. (författare)
  • First measurement of e(+)e(-) -&gt; pK(S)(0)(n)over-barK(-) + c.c. above open charm threshold
  • 2018
  • Ingår i: Physical Review D : covering particles, fields, gravitation, and cosmology. - 2470-0010 .- 2470-0029. ; 98:3
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The process e(+)e(-) -&gt; pK(S)(0)(n) over barK(-) + c.c. and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of 7.4 fb(-1). The Born cross section of e(+)e(-) -&gt; pK(S)(0)(n) over barK(-) + c.c. is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the pK(-), nK(S)(0), pK(S)(0), nK(+), p (n) over bar, or (KSK-)-K-0 invariant mass distributions except for Lambda(1520). The Born cross sections of e(+)e(-) -&gt; Lambda(1520)(n) over barK(S)(0) + c.c. and e(+)e(-) -&gt; Lambda(1520)(p) over barK(+) + c.c. are measured, and the 90% confidence level upper limits on the Born cross sections of e(+)e(-) -&gt; Lambda(1520)(Lambda) over bar (1520) are determined at the seven center-of-mass energies. There is an evident difference in line shape and magnitude of the measured cross sections between e(+)e(-) -&gt; Lambda(1520)(-&gt; pK(-))(n) over barK(S)(0) and e(+)e(-) -&gt; pK-(Lambda) over bar (1520)(-&gt; (n) over barK(S)(0)).</p>
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8.
  • Adare, A., et al. (författare)
  • Centrality dependence of low-momentum direct-photon production in Au plus Au collisions at root s(NN)=200 GeV
  • 2015
  • Ingår i: Physical Review C (Nuclear Physics). - American Physical Society. - 0556-2813. ; 91:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au + Au collisions at root s(NN) = 200 GeV down to pT = 0.4 GeV/c. Photons are detected via photon conversions to e(+)e(-) pairs and an improved technique is applied that minimizes the systematic uncertainties that usually limit direct photon measurements, in particular at low pT. We find an excess of direct photons above the N-coll-scaled yield measured in p + p collisions. This excess yield is well described by an exponential distribution with an inverse slope of about 240 MeV/c in the pT range 0.6-2.0 GeV/c. While the shape of the pT distribution is independent of centrality within the experimental uncertainties, the yield increases rapidly with increasing centrality, scaling approximately with N-part(alpha), where alpha = 1.38 +/- 0.03(stat) +/- 0.07(syst).
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9.
  • Adare, A., et al. (författare)
  • Charged hadron multiplicity fluctuations in Au plus Au and Cu plus Cu collisions from s(NN)=22.5 to 200 GeV
  • 2008
  • Ingår i: Physical Review C (Nuclear Physics). - American Physical Society. - 0556-2813. ; 78:4
  • Tidskriftsartikel (refereegranskat)abstract
    • A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers Au+Au collisions at <radical><radicand>s(NN)</radicand></radical>=62.4 and 200 GeV, and Cu+Cu collisions at <radical><radicand>s(NN)</radicand></radical>=22.5,62.4, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for nondynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon p+p data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. A comparison of the data with a model where hadrons are independently emitted from a number of hadron clusters suggests that the mean number of hadrons per cluster is small in heavy ion collisions.
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10.
  • Adare, A., et al. (författare)
  • Energy loss and flow of heavy quarks in Au+Au collisions at root s(NN) = 200 GeV
  • 2007
  • Ingår i: Physical Review Letters. - American Physical Society. - 1079-7114. ; 98:17
  • Tidskriftsartikel (refereegranskat)abstract
    • The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3 < p(T) < 9 GeV/c at midrapidity (y < 0.35) from heavy-flavor (charm and bottom) decays in Au + Au collisions at root s(NN) = 200 GeV. The nuclear modification factor R-AA relative to p + p collisions shows a strong suppression in central Au + Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v(2) with respect to the reaction plane is observed for 0.5 < p(T) < 5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R-AA and v(2) show a p(T) dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R-AA(p(T)) and v(2)(p(T)) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.
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