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Measurement of Prompt ψ(2S) to J/ψ Yield Ratios in Pb-Pb and p-p Collisions at √s[subscript NN] = 2.76 TeV
Journal article   Open access

Measurement of Prompt ψ(2S) to J/ψ Yield Ratios in Pb-Pb and p-p Collisions at √s[subscript NN] = 2.76 TeV

Vardan Khachatryan, Cécile Caillol, Barbara Clerbaux, Gilles Lentdecker, Didar Dobur, Laurent Favart, Arnaud Gay, Anastasia Grebenyuk, Alexandre Leonard, Abdollah Mohammadi, …
Physical Review Letters, Vol.113, 262301
12/31/2014
DOI: 10.1103/PhysRevLett.113.262301
url
https://doi.org/10.1103/PhysRevLett.113.262301View
Published (Version of record) Open Access

Abstract

The ratio between the prompt $\psi(2\mathrm{S})$ and $\mathrm{J}/\psi$ yields, reconstructed via their decays into $\mu^+\mu^-$, is measured in $\mathrm{Pb}\mathrm{Pb}$ and $\mathrm{p}\mathrm{p}$ collisions at $\sqrt{s_\mathrm{NN}} = 2.76~\mathrm{TeV}$. The analysis is based on $\mathrm{Pb}\mathrm{Pb}$ and $\mathrm{p}\mathrm{p}$ data samples collected by CMS at the LHC, corresponding to integrated luminosities of $150~\mu\mathrm{b}^{-1}$ and $5.4~\mathrm{pb}^{-1}$, respectively. The double ratio of measured yields, $(N_{\psi(2\mathrm{S})} / N_{\mathrm{J}/\psi})_{\mathrm{Pb}\mathrm{Pb}} / (N_{\psi(2\mathrm{S})} / N_{\mathrm{J}/\psi})_{\mathrm{p}\mathrm{p}}$, is computed in three $\mathrm{Pb}\mathrm{Pb}$ collision centrality bins and two kinematic ranges: one at midrapidity, $|y|$ < $1.6$, covering the transverse momentum range $6.5$ < $p_{\mathrm{T}}$ < $30~\mathrm{GeV}/c$, and the other at forward rapidity, $1.6$ < $|y|$ < $2.4$, extending to lower $p_{\mathrm{T}}$ values, $3$ < $p_{\mathrm{T}}$ < $30~\mathrm{GeV}/c$. The centrality-integrated double ratio changes from $0.45 \pm 0.13~\mathrm{(stat)} \pm 0.07~\mathrm{(syst)}$ in the first range to $1.67 \pm 0.34~\mathrm{(stat)} \pm 0.27~\mathrm{(syst)}$ in the second. This difference is most pronounced in the most central collisions. The ratio between the prompt <mml:math display="inline">ψ<mml:mo stretchy="false">(</mml:mo>2S<mml:mo stretchy="false">)</mml:mo></mml:math> and <mml:math display="inline">J<mml:mo stretchy="false">/</mml:mo>ψ</mml:math> yields, reconstructed via their decays into <mml:math display="inline">μ+μ-</mml:math>, is measured in Pb-Pb and <mml:math display="inline">p</mml:math>-<mml:math display="inline">p</mml:math> collisions at <mml:math display="inline">sNN=2.76  TeV</mml:math>. The analysis is based on Pb-Pb and <mml:math display="inline">p</mml:math>-<mml:math display="inline">p</mml:math> data samples collected by CMS at the Large Hadron Collider, corresponding to integrated luminosities of <mml:math display="inline">150  μ<mml:mi mathvariant="normal">b</mml:mi>-1</mml:math> and <mml:math display="inline">5.4  pb-1</mml:math>, respectively. The double ratio of measured yields <mml:math display="inline"><mml:mo stretchy="false">(</mml:mo>Nψ<mml:mo stretchy="false">(</mml:mo>2S<mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">/</mml:mo>NJ<mml:mo stretchy="false">/</mml:mo>ψ<mml:mo stretchy="false">)</mml:mo>Pb-Pb<mml:mo stretchy="false">/</mml:mo><mml:mspace linebreak="goodbreak"/><mml:mo stretchy="false">(</mml:mo>Nψ<mml:mo stretchy="false">(</mml:mo>2S<mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">/</mml:mo>NJ<mml:mo stretchy="false">/</mml:mo>ψ<mml:mo stretchy="false">)</mml:mo>p-p</mml:math> is computed in three Pb-Pb collision centrality bins and two kinematic ranges: one at midrapidity, <mml:math display="inline"><mml:mo stretchy="false">|</mml:mo>y<mml:mo stretchy="false">|</mml:mo><1.6</mml:math>, covering the transverse momentum range <mml:math display="inline">6.5<pT<30  GeV/c</mml:math>, and the other at forward rapidity, <mml:math display="inline">1.6<<mml:mo stretchy="false">|</mml:mo>y<mml:mo stretchy="false">|</mml:mo><2.4</mml:math>, extending to lower <mml:math display="inline">pT</mml:math> values, <mml:math display="inline">3<pT<30  GeV/c</mml:math>. The centrality-integrated double ratio changes from <mml:math display="inline">0.45±0.13<mml:mo stretchy="false">(</mml:mo>stat<mml:mo stretchy="false">)</mml:mo>±0.07<mml:mo stretchy="false">(</mml:mo>syst<mml:mo stretchy="false">)</mml:mo></mml:math> in the first range to <mml:math display="inline">1.67±0.34<mml:mo stretchy="false">(</mml:mo>stat<mml:mo stretchy="false">)</mml:mo>±0.27<mml:mo stretchy="false">(</mml:mo>syst<mml:mo stretchy="false">)</mml:mo></mml:math> in the second. This difference is most pronounced in the most central collisions. The ratio between the prompt psi(2S) and J/psi yields, reconstructed via their decays into muon pairs, is measured in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV. The analysis is based on PbPb and pp data samples collected by CMS at the LHC, corresponding to integrated luminosities of 150 inverse microbarns and 5.4 inverse picobarns, respectively. The double ratio of measured yields, (N[psi(2S)]/N[J/psi])[PbPb] / (N[psi(2S)]/ N[J/psi])[pp], is computed in three PbPb collision centrality bins and two kinematic ranges: one at midrapidity, abs(y) < 1.6, covering the transverse momentum range 6.5 < pt < 30 GeV/c, and the other at forward rapidity, 1.6 < abs(y) < 2.4, extending to lower pt values, 3 < pt < 30 GeV/c. The centrality-integrated double ratio changes from 0.45 +/- 0.13 (stat) +/- 0.07 (syst) in the first range to 1.67 +/- 0.34 (stat) +/- 0.27 (syst) in the second. This difference is most pronounced in the most central collisions.
High Energy Physics Nuclear Physics Physics Experiment Forward rapidity ion collisions Kinematic range Large Hadron Collider (LHC) Nuclear Experiment particle Physique des particules élémentaires relativistic heavy resonance production Tellurium compounds Yield ratios

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