Heavy ion physics at LHCb Jiayin Sun (Tsinghua University) On - PowerPoint PPT Presentation

Heavy ion physics at LHCb Jiayin Sun (Tsinghua University) On behalf of the LHCb collaboration The 21 st Particles & Nuclei International Conference 1-5 September 2017, IHEP, Beijing, China 9/2/2017 PANIC2017 1

Outline • LHCb detector • 𝑞 Pb collisions: recent results • Open heavy flavor results • Hidden heavy flavor results • PbPb collisions: work in progress • Fixed target: first results • Heavy flavor in 𝑞 Ar • Antiproton in 𝑞 He 9/2/2017 PANIC2017 2

LHCb detector • A single arm forward spectrometer designed for the study of particles containing c or b quark. • Acceptance: 2 < 𝜃 < 5 • Vertex detector • IP resolution ~ 20 m m • Tracking system ∆𝑞 • 𝑞 = 0.5% − 1% (5-200 GeV/ c ) • RICH • K/ p /p separation • Electromagnetic + hadronic Calorimeters • Muon systems JINST 3 (2008) S08005 9/2/2017 PANIC2017 3 IJMPA 30 (2015) 1530022

𝑞 Pb datasets and recent results • Rapidity Coverage Forward • 𝑧 ∗ : rapidity in nucleon-nucleon cms • 𝑧 𝑑𝑛𝑡 = ±0.465 𝑞 Pb • Forward: 1.5 < 𝑧 ∗ < 4.0 • Backward: −5.0 < 𝑧 ∗ < −2.5 p Pb • Common region: 2.5 < |𝑧 ∗ | < 4.0 • 𝑡 𝑂𝑂 = 5 TeV (2013) • 𝑞 Pb ( 1.06 nb -1 ) + Pb 𝑞 ( 0.52 nb -1 ) Backward • Open heavy flavor 𝐸 0 and Λ 𝑑 + Pb 𝑞 • Collectivity • 𝑡 𝑂𝑂 = 8 TeV (2016) p Pb • 𝑞 Pb ( 13.6 nb -1 ) + Pb 𝑞 ( 21.8 nb -1 ) • Hidden heavy flavor Τ 𝐾 𝜔 9/2/2017 PANIC2017 4

Prompt 𝐸 0 measurement in 𝑞 Pb at 5TeV PV 𝐿 − 𝐉𝐐 Forward  Backward  𝐸 0 𝜌 + • Reconstructed through decay channel: 𝐸 0 → 𝐿 − 𝜌 + • Inclusive 𝐸 0 mesons from fitting invariant mass dist.: • Signal: Crystal Ball • Background: linear • Prompt 𝐸 0 fraction extracted from fitting impact parameter dist.: • Prompt: simulation • 𝐸 0 -from- b : simulation • Background: sideband in data arXiv:1707.02750 9/2/2017 PANIC2017 5

+ measurement in 𝑞 Pb at 5TeV Prompt Λ 𝑑 PV 𝐿 − 𝐉𝐐 Forward  Backward  + Λ 𝑑 𝜌 + 𝑞 • Reconstructed through decay channel + → 𝑞𝐿 − 𝜌 + Λ 𝑑 + baryons from • Inclusive Λ 𝑑 fitting invariant mass dist.: • Signal: Gaussian • Background: linear + fraction • Prompt Λ 𝑑 extracted from fitting impact parameter dist.: • Prompt: simulation • Λ 𝑑 + -from- b : simulation • Background: sideband in data LHCb-CONF-2017-005 9/2/2017 PANIC2017 6

Prompt 𝐸 0 at 5TeV JHEP 10 (2003) 046 Eur. Phys. J. C77 (2017) 1, nuclear modification factor in 𝑞 Pb Comput. Phys. Commun. 184 (2013) 2562 Comput. Phys. Commun. 198 (2016) 238 𝜏 𝑞Pb (𝑧 ∗ ,𝑞 𝑈 , 𝑡 𝑂𝑂 ) 𝑆 𝑞Pb 𝑧 ∗ , 𝑞 𝑈 = 1 𝐵 × 𝜏 𝑞𝑞 (𝑧 ∗ ,𝑞 𝑈 , 𝑡 𝑂𝑂 ) , A= 208 Updated since preliminary result: Directly measured with prompt 𝐸 0 in 𝑞𝑞 at 𝑡 = 5 TeV arXiv:1610.02230 • Nuclear modification factor smaller at large rapidity • Measurements consistent with theoretical calculations arXiv:1707.02750 9/2/2017 PANIC2017 7

Prompt 𝐸 0 at 5TeV forward-backward production ratio 𝑒𝜏(+ 𝑧 ∗ ,𝑞 𝑈 )/𝑒𝑦 • 𝑆 𝐺𝐶 = 𝑒𝜏(− 𝑧 ∗ ,𝑞 𝑈 )/𝑒𝑦 • 𝑆 𝐺𝐶 does not need results from 𝑞𝑞 collisions. • Compared to next-to-leading order NLO calculations with different nPDFs • Consistent with theoretical calculations within uncertainty arXiv:1707.02750 Comput. Phys. Commun. 184 (2013) 2562 Eur. Phys. J. C77 (2017) 1, Comput. Phys. Commun. 198 (2016) 238 9/2/2017 PANIC2017 8

+ at 5TeV Prompt Λ 𝑑 LHCb-CONF-2017-005 forward-backward production ratio 𝑒𝜏(+ 𝑧 ∗ ,𝑞 𝑈 )/𝑒𝑦 • 𝑆 𝐺𝐶 = 𝑒𝜏(− 𝑧 ∗ ,𝑞 𝑈 )/𝑒𝑦 • 𝑆 𝐺𝐶 does not need results from 𝑞𝑞 collisions. • Compared to next-to-leading order NLO calculations with different nPDFs • Consistent with theoretical calculations within uncertainty Comput. Phys. Commun. 184 (2013) 2562 Eur. Phys. J. C77 (2017) 1, Comput. Phys. Commun. 198 (2016) 238 9/2/2017 PANIC2017 9

Charmed baryon/meson production ratio 𝑆 + 𝐸 0 at 5TeV Τ Λ 𝑑 LHCb-CONF-2017-005 + (𝑧 ∗ ,𝑞 𝑈 ) 𝜏 Λ 𝑑 • 𝑆 + 𝐸 0 = Λ 𝑑 Τ 𝜏 𝐸0 (𝑧 ∗ ,𝑞 𝑈 ) • EPS09LO & EPS09NLO Forward gives similar predictions. • nCTEQ15 slightly lower. • Forward: • Consistent at lower 𝑞 T • Below theory at higher 𝑞 T • Backward: Eur. Phys. J. C77 (2017) 1, Comput. Phys. Commun. 184 Backward • Consistent for all 𝑞 T (2013) 2562 Comput. Phys. Commun. 198 (2016) 238 9/2/2017 PANIC2017 10

Charmed baryon/meson production ratio 𝑆 + 𝐸 0 at 5TeV LHCb-CONF-2017-005 Τ Λ 𝑑 + (𝑧 ∗ ,𝑞 𝑈 ) 𝜏 Λ 𝑑 • 𝑆 + 𝐸 0 = Λ 𝑑 Τ 𝜏 𝐸0 (𝑧 ∗ ,𝑞 𝑈 ) • EPS09LO & EPS09NLO gives similar predictions. • nCTEQ15 slightly lower. • Forward: • Consistent for all |𝑧 ∗ | • Backward: • Consistent at lower |𝑧 ∗ | • Displays a rising trend Eur. Phys. J. C77 (2017) 1, with increasing |𝑧 ∗ | Comput. Phys. Commun. 184 (2013) 2562 Comput. Phys. Commun. 198 (2016) 238 9/2/2017 PANIC2017 11

Prompt and nonprompt Τ 𝐾 𝜔 in p Pb at 8TeV • Reconstructed through arXiv:1706.07122 𝐾 𝜔 → 𝜈 + 𝜈 − Τ • Signal extraction with 2D simultaneous fit to mass and the pseudo proper decay time 𝑢 𝑨 ≡ 𝑨 Τ 𝐾 𝜔 − 𝑨 𝑄𝑊 × 𝑁 Τ 𝐾 𝜔 𝑞 𝑨 • Prompt and nonprompt (from- b - hadrons) separated • Fraction from b hadrons: • Increasing trend • Low 𝑞 T : cold nuclear matter effects different for the prompt and nonprompt 9/2/2017 PANIC2017 12

Prompt Τ 𝐾 𝜔 at 8TeV nuclear modification factor in 𝑞 Pb 𝜏 𝑞Pb (𝑧 ∗ ,𝑞 𝑈 , 𝑡 𝑂𝑂 ) 𝑆 𝑞Pb 𝑧 ∗ , 𝑞 𝑈 = 1 𝐵 × 𝜏 𝑞𝑞 (𝑧 ∗ ,𝑞 𝑈 , 𝑡 𝑂𝑂 ) , A= 208 • pp reference: interpolation of LHCb measurements at 7, 8 and 13TeV • Forward rapidity: suppression up to 50% at low 𝑞 T , decreasing with increasing 𝑞 T • Backward rapidity: closer to unity • Overall agreement with models with large uncertainties on the gluon PDFs at low x • Compatible with 5TeV results arXiv:1706.07122 9/2/2017 PANIC2017 13

Τ 𝐾 𝜔 -from- b -hadrons at 8TeV nuclear modification factor in 𝑞 Pb 𝜏 𝑞Pb (𝑧 ∗ ,𝑞 𝑈 , 𝑡 𝑂𝑂 ) 𝑆 𝑞Pb 𝑧 ∗ , 𝑞 𝑈 = 1 𝐵 × 𝜏 𝑞𝑞 (𝑧 ∗ ,𝑞 𝑈 , 𝑡 𝑂𝑂 ) , A= 208 • pp reference: interpolation of LHCb measurements at 7, 8 and 13TeV • Forward rapidity: smaller suppression up to 30% at low 𝑞 T , reach unity at higher 𝑞 T • Backward: compatible with unity • FONLL with EPS09NLO consistent with data JHEP 04 (2009) 065 arXiv:1706.07122 • Compatible with 5TeV results 9/2/2017 PANIC2017 14

Prompt Τ 𝐾 𝜔 at 8TeV forward-backward production ratio arXiv:1706.07122 𝑒𝜏(+ 𝑧 ∗ ,𝑞 𝑈 )/𝑒𝑦 • 𝑆 𝐺𝐶 = 𝑒𝜏(− 𝑧 ∗ ,𝑞 𝑈 )/𝑒𝑦 • 𝑆 𝐺𝐶 does not need results from 𝑞𝑞 collisions. • Prompt Τ 𝐾 𝜔 : • Clear forward-backward asymmetry • Increasing trend with increasing 𝑞 T • Nonprompt Τ 𝐾 𝜔 : • Closer to unity • Models for prompt Τ 𝐾 𝜔 only • Consistent with 5TeV results 9/2/2017 PANIC2017 15

PbPb collisions • December 2015: first LHCb PbPb data taken 𝑡 𝑂𝑂 = 5 TeV (3-5 m b -1 ) • • Event classification: total energy in the calorimeters (Ecal) • Analyses limited by saturation in Vertex Locator (VELO) • Track reconstruction: 50-100% event activity (~15k clusters) Activity 50-70% 𝐾 𝜔 → 𝜈 + 𝜈 − Τ 𝐸 0 → 𝐿 − 𝜌 + 9/2/2017 PANIC2017 16 https://twiki.cern.ch/twiki/bin/view/LHCb/LHCbPlots2015

Fixed target physics • LHCb: only experiment at the LHC can operate in fixed-target mode • SMOG: The System for Measuring Overlap with Gas • Unique feature • noble gas (He, Ne, Ar …) injection inside the LHC beam close to the interaction point • Luminosity measurement • Internal gas target • Allows p -gas and ion-gas collisions • 𝑡 𝑂𝑂 region between 20 GeV (SPS) and 200 GeV (RHIC) • Access nPDF anti-shadowing region and intrinsic charm content in the nucleon 9/2/2017 PANIC2017 17

Charm production in 𝑞Ar collisions LHCb-CONF-2017-001 • Dataset: JHEP (2013) 2013:122 JHEP (2013) 2013: 155 • 𝑡 𝑂𝑂 = 1 10 GeV (2015) • 6.5 TeV proton beam on Ar gas target • Protons on target: 4 × 10 22 𝐾 𝜔 and ~6500 𝐸 0 • ~500 Τ • Shapes consistent with PYTHIA and interpolation between HERA-B and PHENIX Τ 𝐾 𝜔 Τ Τ 𝐾 𝜔 𝐾 𝜔 𝐸 0 𝐸 0 𝐸 0 9/2/2017 PANIC2017 18

Charm production in 𝑞Ar collisions LHCb-CONF-2017-001 • 𝐾 𝜔 𝐸 0 cross section ratio Τ Τ • Luminosity cancels • Increase with 𝑞 T • Little dependence on rapidity • Demonstrate the feasibility of a heavy−flavor−fixed−target program at LHCb • Theoretical calculations are welcome 9/2/2017 PANIC2017 19

ҧ 𝑞 production in 𝑞He collisions Measurement of ҧ LHCb-CONF-2017-002 • AMS-2: possible anti-proton excess at high energies • 𝑞/𝑞 ratio predictions limited by 𝑞 production cross- uncertainties on ҧ sections, particularly for p -He • Prompt production at 𝑡 𝑂𝑂 = 1 10 GeV in 𝑞 He collisions • EPOS LHC prediction: • Data/MC ~ 1.19 ± 0.08 9/2/2017 PANIC2017 20