Heavy Quarkonium production in p-Pb collisions at LHCb 清华大学高能物理研究中心 Center for High Energy Physics, Tsinghua University Heavy Quarkonium production in p-Pb collisions at LHCb Physics motivation LHCb detector and 𝒑𝐏𝐛 data-taking Asymmetric beam energy 𝑠 𝑁𝑁 =5 TeV rapidity shift Δ𝑦=±0.465 Rapidity coverage (in 𝑁𝑁 c.m.s.) Forward direction (pPb) 1.5<𝑦<4.0 Backward direction (Pbp) −5.0<𝑦<−2.5 Common coverage 2.5< 𝑦 <4.0 pA collisions are important to study cold nuclear matter (CNM) effects Heavy quarkonia production sensitive to CNM effects, which are usually characterized by Forward 𝑝Pb 𝑬 𝒑 =𝟒 𝐓𝐞𝐕 20 Jan. - 10 Feb. 𝑬 𝒑/𝒏 =𝟏.𝟓𝟖 𝐓𝐞𝐕 JHEP 03 (2013) 122 5 TeV 𝒚 𝑹 𝒑𝐏𝐛 (𝒚) 𝚼 𝑱/𝝍 Nuclear modification factor: 𝑅 𝑝A 𝑦, 𝑠 𝑁𝑁 = 1 𝐴 ⋅ d 𝜎 𝑝A d𝑦 𝑦, 𝑠 𝑁𝑁 d 𝜎 𝑝𝑝 d𝑦 𝑦, 𝑠 𝑁𝑁 Forward-backward production ratio: 𝑅 FB 𝑦, 𝑠 𝑁𝑁 = 𝜎 𝑝A + 𝑦 , 𝑠 𝑁𝑁 𝜎 𝑝A − 𝑦 , 𝑠 𝑁𝑁 Backward Low pile-up Integrated ℒ : Forward (pPb) : 1.1 n b −1 Backward (Pbp): 0.4 n b −1 Higher multiplicity in Pbp case as expected Pb𝑝 Pb𝑝 𝑝Pb 𝝍 (′) production and cold nuclear matter effects in 𝒑𝐏𝐛 collisions at 𝒔 𝑵𝑵 = 5 TeV JHEP 02 (2014) 072 JHEP 03 (2016) 033 𝑱/𝝍 cross-sections Forward (𝑝Pb) 𝑝 T [GeV/𝑐] Backward (Pb𝑝) 𝑝 T [GeV/𝑐] Forward (𝑝Pb) 𝑦 Backward (Pb𝑝) −𝑦 Nuclear modification factor 𝑹 𝒑𝐏𝐛 Strong dependence on rapidity 𝐽/𝜓 from 𝑏 less suppressed in forward region than prompt 𝐽/𝜓 ⇒ 𝑏 hadrons less affected by cold nuclear matter effects Prompt 𝜓 2𝑆 more suppressed than prompt 𝐽/𝜓 Theoretical calculations underestimate prompt 𝜓 2𝑆 suppression 𝐽/𝜓 from 𝑏 ( 𝑝 T < 14 GeV) : Prompt 𝜓 (′) Prompt 𝐽/𝜓 ( 𝑝 T < 14 GeV) : 𝝍(𝟐𝐒) cross-sections 𝜓 (′) from 𝑏 Forward (𝑝Pb) Backward (Pb𝑝) Forward (𝑝Pb) Backward (Pb𝑝) Forward-backward production ratio 𝑹 𝐅𝐁 Independent of 𝑝𝑝 cross-sections Part of experimental and theoretical uncertainties cancel Clear difference between prompt 𝐽/𝜓 and 𝐽/𝜓 from 𝑏 Consistent with theoretical calculations 𝜓(2S) from 𝑏 ( 𝑝 T < 14 GeV) : 𝑝 T [GeV/𝑐] 𝑝 T [GeV/𝑐] 𝑦 −𝑦 Prompt 𝜓(2S) ( 𝑝 T < 14 GeV) : Relative suppression of 𝝍(𝟐𝑺) to 𝑱/𝝍 Suppression of prompt 𝜓(2𝑆) stronger than that of prompt 𝐽/𝜓 Same suppression expected for 𝜓(2𝑆) from 𝑏 and 𝐽/𝜓 from 𝑏 𝒃 𝒃 cross-sections 𝚼 production and cold nuclear matter effects in 𝒑𝐏𝐛 collisions at 𝒔 𝑵𝑵 = 5 TeV JHEP 07 (2014) 094 𝑹 𝐅𝐁 for 𝚼(𝟏𝐒) 𝚼 production 𝑹 𝒑𝐏𝐛 for 𝚼(𝟏𝐒) Part of experimental and theoretical uncertainties cancel Agreement with different theoretical models, but statistical uncertainty large Reconstructed using Υ 𝑛𝑆 → 𝜇 + 𝜇 − Forward region: suppression smaller than prompt 𝐽/𝜓, and compatible with 𝑏 hadrons Backward region: indication of antishadowing effect 𝑚 𝜇 + 𝜇 − [MeV/ 𝑐 2 ] Forward 𝑚 𝜇 + 𝜇 − [MeV/ 𝑐 2 ] Backward Systematic uncertainty dominated by mass fit model, data-MC discrepancy and trigger Production ratios 𝑅 𝑛𝑆/1𝑆 ≡ 𝜎 Υ 𝑛𝑆 ×ℬ𝑟(Υ 𝑛𝑆 → 𝜇 + 𝜇 − ) 𝜎 Υ 1𝑆 ×ℬ𝑟(Υ 1𝑆 → 𝜇 + 𝜇 − ) 清华大学高能物理研究中心