Measurement of the J / and (2 S ) cross section in pp collisions at - PowerPoint PPT Presentation

Measurement of the J /ψ and ψ (2 S ) cross section in pp collisions at √ s = 13 TeV Heber Zepeda Fern´ andez Advisor: Dr. Alberto S´ anchez Hern´ andez CINVESTAV, CMS http://inspirehep.net/record/1447964 May 24, 2017 1 / 21

Outline Introduction 1 Measurement of the cross section 2 Conclusions 3 2 / 21

Introduction Introduction 3 / 21

Introduction Introduction: Prompt and Non prompt production Let’s take a J /ψ for the example. No prompt No prompt µ Prompt Prompt µ J/ ψ J/ ψ µ µ d 4 / 21 Figure: Prompt and no-prompt production of J /ψ .

Introduction Introduction: How is it possible? ? C C Figure: J /ψ from proton-proton collision. 5 / 21

Introduction Introduction: Explaining production NRQCD factorization: Short-distance (Color Singlet Model) and long-distance (Color Octet Model). The two steps of quarkonium production. The initial Q Q in t and the final state t is the bound QQ BS state. 6 / 21

Introduction Introduction: Explaining production Several models: Color-Singlet Model Figure: NLO and NNLO*CS contributions at (left) √ s = 1 . 96 TeV and (right) √ s = 7 TeV. Taken from Journal of Physics G: Nuclear and Particle Physics, 38, Number 12. 7 / 21

Introduction The Compact Muon Solenoid (CMS) Figure: The incredible CMS detector 8 / 21

Introduction Introduction: High energy (7 TeV) at LHC: CMS Figure: The J /ψ and ψ (2 S ) differential p T cross sections times the dimuon branching fractions for four rapidity bins and integrated over the range | y | < 1 . 2. Taken from Phys. Rev. Lett. 114, 191802 9 / 21

Introduction Before the unknown, the known. It was necessary to re-discovered. Figure: Different masses can be reconstructed using CMS tracking. 10 / 21

Measurement of the cross section Measurement of the cross section 11 / 21

Measurement of the cross section Cross section The differential cross section is given by: dp T dy = N c ¯ d 2 σ c ( p T , y ) 1 � � Br ( ψ → µµ ) · , (1) L ∆ y ∆ p T ǫ ( p T , y ) A ( p T , y ) The measurement: 2.4 fb − 1 for J /ψ and 2.7 fb − 1 for ψ (2 S ) 20 GeV < p T ∼ 120 GeV and | y | < 1.2 (increasing 0.3) for both particles. 12 / 21

Measurement of the cross section Measurement of the yields N ( c ¯ c ) Mass fit: Different PDF function for J /ψ and ψ (2 S ). Lifetime fit: To separate Prompt and No-Prompt. As example, Figure: Mass fit (left) and lifetime fit (right) for J / psi in a particular y and p T bin. 13 / 21

Measurement of the cross section Acceptance and efficiency Acceptance We used Monte Carlo simulation. N gen | kin ( p T , y ) A ( p T , y ) = N gen ( p T , y ) . (2) Efficiency We used data. ǫ µµ ( p T , y ) = ǫ ( p T 1 , η 1 ) · ǫ ( p T 2 , η 2 ) · ρ ( p T , y ) · ǫ 2 (3) tk All efficiencies from data. ǫ ( p T i , η i ) = ǫ reco · ǫ L 1 L 2 · ǫ L 3 , from TnP technique. ǫ µµ = Reconstructed / Accepted. 14 / 21

Measurement of the cross section Systematic uncertainties Uncertainties in the estimation of the yield. Statistical. Non-prompt fraction statistical. Acceptance statistical. MC. Statistic of sample. Reconstruction efficiency. Single muon efficiency. Dimuon orrelation ( ρ ). Rapidity integrated range. 15 / 21

Measurement of the cross section Measurement of cross section We have all the numbers of dp T dy = N c ¯ d 2 σ c ( p T , y ) 1 � � Br ( ψ → µµ ) · , (4) L ∆ y ∆ p T ǫ ( p T , y ) A ( p T , y ) So, we can calulate the cross section: 16 / 21

Measurement of the cross section Measurement of cross section: Prompt J /ψ and ψ (2 S ) -1 2.4 fb (13 TeV) [pb/GeV] 3 10 0.0 < |y| < 0.3 CMS × Preliminary 0.3 < |y| < 0.6 1/2 2 × dy 10 0.6 < |y| < 0.9 1/4 σ 2 T -1 d dp × 2.7 fb (13 TeV) 0.9 < |y| < 1.2 1/8 [pb/GeV] × 0.0 < |y| < 0.3 10 CMS BR × 0.3 < |y| < 0.6 1/2 10 Preliminary × 0.6 < |y| < 0.9 1/4 dy 1 σ × 1 0.9 < |y| < 1.2 1/8 2 T d dp × BR − − 1 1 10 10 − 2 10 − 2 10 ψ J/ − 3 10 − 3 10 ψ (2S) − 4 10 2 20 30 40 50 60 70 80 90 10 2 20 30 40 50 60 70 80 90 10 ψ ψ J/ (2S) p [GeV] p [GeV] T T Figure: Prompt cross section times branching ratios for the J /ψ (left) and ψ (2 S )(right) in several rapidity ranges for the barrel trigger. 17 / 21

Measurement of the cross section Measurement of the Cross section ψ ψ J/ (2S) -1 -1 2.4 fb | 2.7 fb (13 TeV) 4 10 [pb/GeV] ψ J/ s = 13 TeV CMS 3 10 ψ Preliminary (2S) s = 7 TeV 2 10 dy |y| < 1.2 σ 2 ψ ψ T J/ -1 (2S) -1 d dp 2.4 fb | 2.7 fb (13 TeV) 10 0.16 (2S) ψ ψ ψ (2S) / J/ × J/ CMS BR ψ 1 σ σ 0.14 |y| < 1.2 × Preliminary × BR BR − 1 10 0.12 − 2 10 0.1 − 3 10 0.08 4 0.06 13 TeV 7 TeV 3 0.04 2 0.02 1 2 20 30 40 50 60 70 80 90 10 2 20 30 40 50 60 70 80 90 10 ψ (nS) p [GeV] p [GeV] T T Figure: (left) Prompt cross sections times branching ratios for the J /ψ Comparison of 7 TeV and 13 TeV cross sections. (right) Cross section ratios ψ (2 S ) / J /ψ (right). 18 / 21

Measurement of the cross section Measurement of the Cross section Figure: (Comparison of the non-prompt fraction of J /ψ (left) and ψ (2 S ) (right) as a function of dimuon pT for 13 TeV and 7 TeV. 19 / 21

Conclusions Conclusions The differential production of J /ψ and ψ (2 S ) cross section have been measured in pp collisions at √ s = 13 TeV with the CMS detector at the LHC. This measurement has been performed in central rapidity region ( | y | < 1 . 2) as function of p T in several rapidity region. We studied the p T from 20 GeV to 120 GeV. We could make the ratios of cross sections measured at 13 TeV and 7 TeV. The complete result will be public in few weeks. References CMS-PAS-BPH-15-005, http : // inspirehep . net / record / 1447964 20 / 21

Conclusions Thanks References CMS-PAS-BPH-15-005, http : // inspirehep . net / record / 1447964 21 / 21