CMS-HIN-16-004 ; CERN-EP-2016-258 | ||
Relative modification of prompt $ {\psi\mathrm{(2S)}} $ and $\mathrm{J}/\psi $ yields from pp to PbPb collisions at ${\sqrt{s_{\mathrm{NN}}}} = $ 5.02 TeV | ||
CMS Collaboration | ||
4 November 2016 | ||
Phys. Rev. Lett. 118 (2017) 162301 | ||
Abstract: The relative modification of the prompt ${\psi\mathrm{(2S)}} $ and $\mathrm{J}/\psi $ yields from pp to PbPb collisions, at the center of mass energy of 5.02 TeV per nucleon pair, is presented. The analysis is based on pp and PbPb data samples collected by the CMS experiment at the LHC in 2015, corresponding to integrated luminosities of 28.0 pb$^{-1}$ and 464 $\mu$b$^{-1}$, respectively. The double ratio of measured yields of prompt charmonia reconstructed through their decays into muon pairs, $(N_{{\psi\mathrm{(2S)}} }/N_{\mathrm{J}/\psi })_{\mathrm{PbPb }}/ (N_{{\psi\mathrm{(2S)}} }/N_{\mathrm{J}/\psi })_{\mathrm{pp}}$, is determined as a function of PbPb collision centrality and charmonium transverse momentum $p_{\mathrm{T}}$, in two kinematic intervals: $|{y}| < $ 1.6 covering 6.5 $ < p_{\mathrm{T}} <$ 30 GeV/$c$ and 1.6 $ < |{y}| < $ 2.4 covering 3 $ < p_{\mathrm{T}} < $ 30 GeV/$c$. The centrality-integrated double ratios are 0.36 $\pm$ 0.08 (stat) $\pm$ 0.05 (syst) in the first interval and 0.24 $\pm$ 0.22 (stat) $\pm$ 0.09 (syst) in the second. The double ratio is lower than unity in all the measured bins, suggesting that the ${\psi\mathrm{(2S)}}$ yield is more suppressed than the $\mathrm{J}/\psi$ yield in the explored phase space. | ||
Links: e-print arXiv:1611.01438 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; |
Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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Figures | |
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Figure 1:
Invariant mass spectrum of ${\mu^+ \mu^- }$ pairs (restricting to the ${\psi \mathrm {(2S)}}$ region in the insets) in PbPb collisions for (left) $ {| y | }< $ 1.6, 9 $ < {p_{\mathrm {T}}} < $ 12 GeV/$c$, all centrality, and (right) 1.6 $ < {| y | }< $ 2.4, 3 $ < {p_{\mathrm {T}}} < $ 30 GeV/$c$, 0-20% centrality. The results of the fits described in the text are also shown. |
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Figure 1-a:
Invariant mass spectrum of ${\mu^+ \mu^- }$ pairs (restricting to the ${\psi \mathrm {(2S)}}$ region in the insets) in PbPb collisions for $ {| y | }< $ 1.6, 9 $ < {p_{\mathrm {T}}} < $ 12 GeV/$c$, all centrality. The results of the fits described in the text are also shown. |
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Figure 1-b:
Invariant mass spectrum of ${\mu^+ \mu^- }$ pairs (restricting to the ${\psi \mathrm {(2S)}}$ region in the insets) in PbPb collisions for 1.6 $ < {| y | }< $ 2.4, 3 $ < {p_{\mathrm {T}}} < $ 30 GeV/$c$, 0-20% centrality. The results of the fits described in the text are also shown. |
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Figure 2:
Transverse momentum dependence of ${(N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm {PbPb}} } / (N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm{ p } \mathrm{ p } } }} $, for mid (squares) and forward (circles) rapidity, with both muons above the ${p_{\mathrm {T}}}$ threshold described in the text. The arrow represents the 95% CL interval in the bin where the measurement is consistent with 0. The vertical lines (boxes) represent the statistical (systematic) uncertainties. The horizontal lines represent the width of the ${p_{\mathrm {T}}}$ bins. |
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Figure 3:
Event centrality dependence of ${(N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm {PbPb}} } / (N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm{ p } \mathrm{ p } } }} $, for mid (left) and forward (right) rapidity, with both muons above the ${p_{\mathrm {T}}}$ threshold described in the text. Values for the centrality-integrated sample are given in the right panels. The arrows represent 95% CL intervals in the bins where the measurement is consistent with 0. The vertical lines (boxes) represent the statistical (systematic) uncertainties. The statistical and systematic uncertainties in the ${\mathrm{ p } \mathrm{ p } }$ measurements, common to all points, are represented as boxes at unity. The measurements from CMS at $ {\sqrt {s_{_{\mathrm {NN}}}}} = $ 2.76 TeV [13] are also shown. |
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Figure 3-a:
Event centrality dependence of ${(N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm {PbPb}} } / (N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm{ p } \mathrm{ p } } }} $, for mid rapidity, with both muons above the ${p_{\mathrm {T}}}$ threshold described in the text. Values for the centrality-integrated sample are given in the right panels. The arrows represent 95% CL intervals in the bins where the measurement is consistent with 0. The vertical lines (boxes) represent the statistical (systematic) uncertainties. The statistical and systematic uncertainties in the ${\mathrm{ p } \mathrm{ p } }$ measurements, common to all points, are represented as boxes at unity. The measurements from CMS at $ {\sqrt {s_{_{\mathrm {NN}}}}} = $ 2.76 TeV [13] are also shown. |
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Figure 3-b:
Event centrality dependence of ${(N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm {PbPb}} } / (N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm{ p } \mathrm{ p } } }} $, for forward rapidity, with both muons above the ${p_{\mathrm {T}}}$ threshold described in the text. Values for the centrality-integrated sample are given in the right panels. The arrows represent 95% CL intervals in the bins where the measurement is consistent with 0. The vertical lines (boxes) represent the statistical (systematic) uncertainties. The statistical and systematic uncertainties in the ${\mathrm{ p } \mathrm{ p } }$ measurements, common to all points, are represented as boxes at unity. The measurements from CMS at $ {\sqrt {s_{_{\mathrm {NN}}}}} = $ 2.76 TeV [13] are also shown. |
Tables | |
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Table 1:
Transverse momentum dependence of the double ratio ${(N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm {PbPb}} } / (N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm{ p } \mathrm{ p } } }} $, for mid-rapidity ($ {| y | }< $ 1.6) and forward rapidity (1.6 $ < {| y | } < $ 2.4), with both muons within the CMS acceptance. The 95% CL intervals are also given. |
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Table 2:
Event centrality dependence of the double ratio ${(N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm {PbPb}} } / (N_{ {\psi \mathrm {(2S)}} }/ N_{{\mathrm{J}/\psi } })_{ {\mathrm{ p } \mathrm{ p } } }} $, for two kinematic ranges, with both muons within the CMS acceptance. The 95% CL intervals are also given. |
Summary |
In summary, the double ratio $(N_{{\psi\mathrm{(2S)}} }/N_{\mathrm{J}/\psi })_{\mathrm{PbPb }}/ (N_{{\psi\mathrm{(2S)}} }/N_{\mathrm{J}/\psi })_{\mathrm{pp}}$ was measured to compare the relative production of $\mathrm{J}/\psi $ and ${\psi\mathrm{(2S)}} $ mesons in pp and PbPb collisions at ${\sqrt{s_{\mathrm{NN}}}} = $ 5.02 TeV, as a function of transverse momentum and collision centrality. The double ratio is below unity in all bins, suggesting that the ${\psi\mathrm{(2S)}} $ yield is more suppressed than the $\mathrm{J}/\psi $ yield in the kinematic range explored. The 5.02 TeV data do not show the enhancement in the double ratio previously seen for collisions at 2.76 TeV in the 1.6 $ < |{y}| < $ 2.4 and 3 $ < p_{\mathrm{T}} < $ 30 GeV/$c$ range. No strong variations are observed with charmonium $p_{\mathrm{T}}$ or collision centrality. These results should significantly contribute to a deeper understanding of the medium effects influencing in $\mathrm{J}/\psi $ and ${\psi\mathrm{(2S)}} $ production. |
Additional Figures | |
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Additional Figure 1:
Invariant mass spectrum of $\mu ^+\mu ^-$ pairs (restricting to the $ {\psi \text {(2S)}} $ region in the insets) in pp collisions for $ |y| < $ 1.6, 6.5 $ < p_\text {T}< $ 30 GeV/$c$. |
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Additional Figure 2:
Invariant mass spectrum of $\mu ^+\mu ^-$ pairs (restricting to the $ {\psi \text {(2S)}} $ region in the insets) in pp collisions for 1.6 $ < |y| < $ 2.4, 3 $ < p_\text {T} < $ 30 GeV/$c$. |
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Additional Figure 3:
Invariant mass spectrum of $\mu ^+\mu ^-$ pairs (restricting to the $ {\psi \text {(2S)}} $ region in the insets) in PbPb collisions for $ |y |< $ 1.6, 6.5 $ < p_\text {T}< $ 30 GeV/$c$, all centrality. |
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Additional Figure 4:
Invariant mass spectrum of $\mu ^+\mu ^-$ pairs (restricting to the $ {\psi \text {(2S)}} $ region in the insets) in PbPb collisions for 1.6 $ < |y| < $ 2.4, 3 $ < p_\text {T} < $ 30 GeV/$c$, all centrality. |
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Additional Figure 5:
Event centrality dependence of $(N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{ {\text {PbPb}} } / (N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{{ {\mathrm{ p } \mathrm{ p } }} }$ with both muons above the $p_\text {T}$ threshold described in the text. Values for the centrality-integrated sample are given in the right panel. Arrows represent 95% CL intervals in the bins where the measurement is consistent with 0. Vertical lines (boxes) represent the statistical (systematic) uncertainties. The statistical and systematic uncertainties in the pp measurements, common to all points, are represented as boxes at unity. |
png pdf |
Additional Figure 6:
Transverse momentum dependence of $(N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{ {\text {PbPb}} } / (N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{{ {\mathrm{ p } \mathrm{ p } }} }$, for mid (squares) and forward (circles) rapidity, with both muons above the $p_\text {T}$ threshold described in the text. The arrow represents the 95% CL interval in the bin where the measurement is consistent with 0. Vertical lines (boxes) represent the statistical (systematic) uncertainties. Horizontal lines represent the width of the $p_\text {T}$ bins. The bands represent the predictions from the model of X.Du and R.Rapp [1] (updated from Ref. [2]). |
png pdf |
Additional Figure 7:
Event centrality dependence of $(N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{ {\text {PbPb}} } / (N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{{ {\mathrm{ p } \mathrm{ p } }} }$, for midrapidity, with both muons above the $p_\text {T}$ threshold described in the text. Values for the centrality-integrated sample are given in the right panels. Arrows represent 95% CL intervals in the bins where the measurement is consistent with 0. Vertical lines (boxes) represent the statistical (systematic) uncertainties. The statistical and systematic uncertainties in the pp measurements, common to all points, are represented as boxes at unity. The measurements from CMS at $\sqrt {s_{_{\text {NN}}}} = $ 2.76 TeV [3] are also shown. The hashed boxes represent the predictions from the model of X.Du and R.Rapp [1] (updated from Ref. [2]). |
png pdf |
Additional Figure 8:
Event centrality dependence of $(N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{ {\text {PbPb}} } / (N_{ {\psi \text {(2S)}} }/ N_{{ \mathrm{J}/\psi } })_{{ {\mathrm{ p } \mathrm{ p } }} }$, for forward rapidity, with both muons above the $p_\text {T}$ threshold described in the text. Values for the centrality-integrated sample are given in the right panels. Arrows represent 95% CL intervals in the bins where the measurement is consistent with 0. Vertical lines (boxes) represent the statistical (systematic) uncertainties. The statistical and systematic uncertainties in the pp measurements, common to all points, are represented as boxes at unity. The measurements from CMS at $\sqrt {s_{_{\text {NN}}}} = $ 2.76 TeV [3] are also shown. The hashed boxes represent the predictions from the model of X.Du and R.Rapp [1] (updated from Ref. [2]). |
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Compact Muon Solenoid LHC, CERN |