LHCb overview. Francesco Bossù on behalf of the LHCb collaboration. Laboratoire de l Accélérateur Linéaire, Orsay

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1 LHCb overview Francesco Bossù on behalf of the LHCb collaboration Laboratoire de l Accélérateur Linéaire, Orsay Rencontres QGP-France 16 Étretat, -13 Oct 16

2 LHCb detector ˆ Single arm spectrometer, fully instrumented in < y < 5 ˆ Designed for heavy flavor physics, it is becoming a general purpose detector JINST 3 (8) S85 IJMPA 3 (15) 153 Excellent vertex, IP and decay time resolution ˆ σ(ip) µm for high-p T tracks ˆ σ(τ) 45fs for Bs J/ψφ decays Very good momentum resolution ˆ δp/p.5 1% for < p < GeV/c Particle identification ˆ ɛ K K 95% for ɛ π K 5% up to GeV/c ˆ ɛ µ µ 97% for ɛ π µ 1 3% Dipole magnet ˆ bending power: 4 T m F. Bossù LHCb overview Étretat, -13 Oct 16 1 / 19

3 LHCb detector ˆ LHCb fully instrumented in < y < 5 ˆ Collider mode: Complementary to other LHC experiments ˆ Data taking in fixed target mode: unique feature! F. Bossù LHCb overview Étretat, -13 Oct 16 / 19

4 LHCb detector as Fixed Target experiment SMOG: System for Measuring Overlap with Gas Noble gases injected in the VeLo region Designed and used for luminosity measurements Allows measurement of p- or Pb-Gas collisions Precise vertexing allows to separate beam-beam and beam-gas contributions F. Bossu LHCb overview E tretat, -13 Oct 16 3 / 19

5 LHCb running modes Kinematic coverage in rest frame ˆ Collider: forward/backward rapidities ˆ Fixed target: mid and backward rapidities, energies between SPS and RHIC LHCb bridges the gap from SPS to LHC in a single experiment y : rapidty in the centre of mass frame F. Bossù LHCb overview Étretat, -13 Oct 16 4 / 19

6 LHCb physics programme Nucleus-Nucleus ˆ Characterization of the Quark Gluon Plasma: ˆ Measurements of quarkonia states (including χ c ) and open heavy flavours down to zero p T ˆ Possibility to disentangle prompt and from-b components ˆ Dynamic of the medium and hadronization process ˆ Total cross section, energy flow, particle multiplicity and correlations ˆ Ultra-peripheral collisions to probe gluon shadowing in nuclei at low-x proton-nucleus ˆ Study of cold nuclear matter effects ˆ Study modifications of parton distribution function in nuclei ˆ Investigate possible collective phenomena in high-activity events... both in collider and in fixed target mode F. Bossù LHCb overview Étretat, -13 Oct 16 5 / 19

7 LHCb data taking 13: ppb and Pbp runs ˆ 1.6 nb 1 of data 15: PbPb run ˆ 5 µb 1 of data (luminosity calibration in progress) Fixet target mode Projectile Target snn (GeV) Duration p Ne 87 3 min (1) Pb Ne 54 3 min (13) p Ne 1 1 h (15) p He 1 8 h (15) p Ar 1 3 days(15) p Ar 69 few hours (15) Pb Ar weeks (15) p He 1 days (16) F. Bossù LHCb overview Étretat, -13 Oct 16 6 / 19

8 p-pb collisions at s NN = 5 TeV See Michael s talk on Tuesday!! ˆ Goal: study nuclear matter effects ˆ Two-particle angular correlations ˆ Long range correlation measurements in Pb-Pb collisions interpreted as hydrodynamical flow of deconfined medium ˆ Mid-rapidity measurements showed the ridge in p-pb collisions. LHCb forward rapidity coverage is unique. ˆ Open and hidden heavy-flavours: ˆ Produced in initial hard scatterings ˆ Essential tools to study cold nuclear matter effects (CNM) ˆ p-pb measurements essential to disentangle QGP from CNM effects in AA collisions ˆ 1.6 nb 1 collected in 13. ˆ p and Pb beams reversal allows to study backward and forward rapidity regions ˆ Asymmetry in beam energies: rapidity coverage shifted by y < y < < y <.5 F. Bossù LHCb overview Étretat, -13 Oct 16 7 / 19

9 p-pb - Two particle angular correlations Measurement of angular ( φ, η)-correlations of prompt charged particles Low activity (5-%) High activity (-3%) p-pb (forward) Events Activity class 5 % (low) 3 5% (med/low) 3% (med/high) % (high) 3% (very high) LHCb p+pb s NN = 5 TeV hit N VELO Pb-p (backward) Events Activity class 5 % (low) 3 5% (med/low) 3% (med/high) % (high) 3% (very high) LHCb Pb+p s NN = 5 TeV hit N VELO arxiv: In high activity events, near side ridge ( φ = ) visible F. Bossù LHCb overview Étretat, -13 Oct 16 8 / 19

10 p-pb - J/ψ, ψ(s) and Υ(1S) ˆ Candidates fully reconstructed from well identified muons ˆ Prompt J/ψ, ψ(s) and those from b decays separated using pseudo-proper decay time JHEP 7 (14) 94 JHEP 14 (14) 7 JHEP 163 (16) 133 Forward rapidity ˆ Significant suppression for J/ψ, even larger for ψ(s) ˆ Modest suppression for non-prompt J/ψ, similar to Υ(1S) Backward rapidity ˆ No suppression for J/ψ and Υ(1S) ˆ Unexpected large suppression for ψ(s), not described by E.loss and shadowing J/ψ and Υ(1S) results reproduced by models F. Bossù LHCb overview Étretat, -13 Oct 16 9 / 19

11 p-pb - Prompt D and Z boson Prompt D production Z boson production [nb] σ Z µ + µ 4 3 syst. LHCb syst. stat. ppb s NN = 5 TeV FEWZ NNLO + MSTW8 FEWZ NNLO + MSTW8 + EPS9 (NLO) backward forward ˆ Measurement down to zero p T ˆ Clear asymmetry forward/backward ˆ No p T dependence ˆ Asymmetry more important at larger y ˆ Within uncertainties, data are reproduced by pqcd calculations with EPS9 npdf LHCb-CONF-16-3 ˆ Limited statistics ˆ Electroweak bosons are sensible probes for investigating PDF modifications in nuclei F. Bossù LHCb overview Étretat, -13 Oct 16 / 19

12 First glimpse at PbPb data ˆ December 15. First time of LHCb participation in Pb-Pb data taking ˆ Up to 54 colliding bunches. Luminosity 3-5 µb 1 ˆ Minimum bias trigger configuration: all inelastic interactions recorded on tape Example of one PbPb event with more than charged tracks and a J/ψ candidate F. Bossù LHCb overview Étretat, -13 Oct / 19

13 PbPb - Centrality determination - ongoing ˆ Experimental observables: total energy in the calorimeters, EM (Ecal) or hadronic (Hcal) ˆ No saturation of calorimeter signals even for most central collisions Entries [a.u.] 5 4 s NN = 5 TeV 3 4-5% 3-4% -3% -% -% Ecal Energy [TeV] Number of Velo Clusters = 5 TeV s NN Ecal Energy [TeV] ˆ Event classification in terms of Ecal activity ˆ Saturation in Vertex Locator (VELO) clearly visible. Track reconstruction was performed up to 15k clusters ˆ Corresponding range: 5-% event activity F. Bossù LHCb overview Étretat, -13 Oct 16 1 / 19

14 PbPb - Looking for heavy signals... J/ψ µ + µ Candidates per 8. MeV/c = 5 TeV s NN 7%<Event Activity<9% Candidates per 8. MeV/c 5 5%<Event Activity<7% s NN = 5 TeV M(µµ) [MeV/c ] D K π + Candidates per 8. MeV/c = 5 TeV s NN 7%<Event Activity<9% Candidates per 8. MeV/c M(µµ) [MeV/c ] = 5 TeV s NN 5%<Event Activity<7% M(Kπ) [MeV/c ] M(Kπ) [MeV/c ] Clear signals also in 5-7% event activity bin F. Bossù LHCb overview Étretat, -13 Oct / 19

15 PbPb - Looking for strange signals... K S π+ π 7%<Event Activity<9% s NN = 5 TeV 8 Candidates per 1. MeV/c 6 4 Candidates per 1. MeV/c = 5 TeV s NN 5%<Event Activity<7% Λ pπ + Candidates per.3 MeV/c M(ππ) [MeV/c ] 7%<Event Activity<9% 18 s NN = 5 TeV M(pπ) [MeV/c ] Candidates per.3 MeV/c M(ππ) [MeV/c ] = 5 TeV s NN 5%<Event Activity<7% M(pπ) [MeV/c ] F. Bossù LHCb overview Étretat, -13 Oct / 19

16 PbPb - J/ψ in ultra-peripheral collisions Selection: nothing in the detector but two muon tracks Candidates per 8. MeV/c = 5 TeV s NN M(µµ) [MeV/c ] Candidates per.8 (GeV/c) 1 = 5 TeV s NN.1..3 p ( µ + µ - ) [GeV/c) ] T p 1 (µµ) [(GeV/c) T ] ˆ Candidates of coherent photo-produced J/ψ in PbPb ultra peripheral collisions ˆ These studies will benefit of the new Herschel detector ˆ Possibility to define large rapidity gaps: 5 < y < 9 ˆ Herschel was taking data in 15 F. Bossù LHCb overview Étretat, -13 Oct / 19

17 Fixed-target - p-ne ˆ J/ψ and open charm production in p-ne at s NN = 1 GeV ˆ About 1 hours of data taking J/ψ µ + µ D K π + entries / 16 MeV/c pne data entries / 8 MeV/c pne data µ + µ invariant mass (MeV/c ) π K invariant mass (MeV/c ) ˆ Clear signals ˆ Luminosity determination is challenging: based on pe elastic scattering F. Bossù LHCb overview Étretat, -13 Oct / 19

18 DataMM Entries 1395 Mean 186 RMS 48.8 Fixed-target - p-ar ˆ J/ψ and open charm production in p-ar at s NN = 1 GeV ˆ About 3 days of data taking J/ψ µ + µ D K π + Entries / 8 MeV/c 1 8 Total sample 44 ± 1 J/ψ candidates 15 par data Entries / 8 MeV/c 5 15 par data ± 95 D Total sample candidates µ + µ invariant mass [MeV/c] ˆ Clear signals K π + invariant mass [MeV/c] ˆ Luminosity determination is challenging: based on pe elastic scattering F. Bossù LHCb overview Étretat, -13 Oct / 19

19 ˆ High energy neutrino physics: backgrounds from charm production. ˆ Possibility to study with LHCb intrinsic charm at large x F. Bossù LHCb overview Étretat, -13 Oct / 19 Fixed-target - Link with cosmic ray physics ˆ AMS- results show a possible excess of antiprotons with respect to secondary production in the interstellar medium (pp px and phe px ) ˆ Possible evidence for Dark Matter contribution JCAP 159 (15) no.9, 3 ˆ Largest uncertainty: σ(phe px ) ˆ LHC proton beam on He at rest, good energy range for cross section measurements

20 Summary ˆ LHCb demonstrated that it can play an important role in heavy ion physics ˆ Successful data taking in ppb collisions at s NN = 5 TeV in 13 ˆ Two-particle angular correlations: similar behaviour backward-forward rapidities in absolute event activity classes ˆ Cold nuclear matter effects visible in heavy quarkonia and open charm measurements ˆ PbPb collisions collected in 15 ˆ For the moment, measurements will be carried out for peripheral and ultra-peripheral collisions ˆ Clear physics signals, analysis ongoing ˆ Fixed-target physics ˆ Unique feature!! ˆ Exploiting colliding system of different sizes and energies More to come: ˆ Looking forward to collecting ppb collisions at s NN = 5 and 8 TeV in 16 ˆ At 8 TeV, x more statistics with respect to previous ppb run ˆ Possibility to study more observables (Υ(3S), Drell-Yan, associated J/ψ -D, W boson...) ˆ In the meanwhile, additional fixed target campaigns are foreseen. Stay tuned! F. Bossù LHCb overview Étretat, -13 Oct / 19

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22 p-pb - Z boson Candidates / ( GeV/c ) LHCb ppb s NN = 5 TeV backward LHCb ppb s NN = 5 TeV Candidates / ( GeV/c ) LHCb ppb s NN = 5 TeV forward LHCb ppb s NN = 5 TeV m [GeV/c µ + µ ] m [GeV/c µ + µ ] σ [nb] Z µ + µ 4 3 syst. LHCb syst. stat. ppb s NN = 5 TeV FEWZ NNLO + MSTW8 FEWZ NNLO + MSTW8 + EPS9 (NLO) backward forward ˆ Clean signal: 11 forward candidates, 4 backward candidates ˆ Cross sections in agreement with predictions, although the production of Z in the backward region appears slightly higher than prediction

23 p-pb - Prompt D Events / (.1 ) = 5 TeV s NN Forward Data Signal+Bkg Signal Bkg D -from-b ) Events/(4 MeV/c = 5 TeV s NN Forward Events / (.1 ) = 5 TeV s NN Backward 4 log(χ )) Data Signal+Bkg Signal Bkg D -from-b (D IP log(χ )) (D IP ) Events/ (4 MeV/c M(K π + ) [MeV/c 3 = 5 TeV s NN Backward M(K π + ) [MeV/c ] ]

24 p-pb - Prompt J/ψ ) Candidates / (5 MeV/c (a) LHCb ppb(fwd) s NN = 5 TeV.5 < y < 3. p < 14 GeV/c T [MeV/c ] m µµ Candidates / (. ps) (c) LHCb ppb(fwd) s NN = 5 TeV.5 < y < 3. p < 14 GeV/c T t z [ps] ) Candidates / (5 MeV/c (b) LHCb ppb(bwd) s NN = 5 TeV 4. < y < 3.5 p < 14 GeV/c T Candidates / (. ps) (d) LHCb ppb(bwd) s NN = 5 TeV 4. < y < 3.5 p < 14 GeV/c T [MeV/c ] m µµ t z [ps]

25 p-pb - Prompt ψ(s) Candidates / ( MeV/c ) LHCb 1.5 < y < 4. 5 ppb(fwd) s NN = 5 TeV p < 14 GeV/c T 15 Candidates / ps 4 3 LHCb ppb(fwd) s NN = 5 TeV 1.5 < y < 4. p < 14 GeV/c T M [MeV/c µµ ] -5 5 t z [ps] Candidates / ( MeV/c ) LHCb 5. < y <.5 ppb(bwd) s NN = 5 TeV p < 14 GeV/c T Candidates / ps 4 3 LHCb ppb(bwd) s NN = 5 TeV 5. < y <.5 p < 14 GeV/c T M [MeV/c µµ ] -5 5 t z [ps]

26 p-pb - J/ψ, ψ(s) and Υ(1S) ˆ Candidates fully reconstructed from well identified muons ˆ Prompt J/ψ, ψ(s) and those from b decays separated using pseudo-proper decay time JHEP 7 (14) 94 JHEP 14 (14) 7 JHEP 163 (16) 133 Models ˆ EPS9LO (CSM): PRC88 (13) 4791; NPA 96 (14) 36 ˆ EPS9LNO (shadowing + CEM): IJMP E (13) 1337 ˆ Energy Loss: JHEP 3 (13) 1; JHEP 5 (13) 155 ˆ ndsg LO: PRC88 (13) 4791

27 p-pb - Two particle angular correlations Y( φ) CZYAM ˆ φ projections away from the jet peak ( < η <.9) ˆ Subtraction of the Zero Yield At Minimum (ZYAM) ˆ Near side correlation increases with the event activity ˆ More evident in Pb-p collisions (backward) ˆ Absolute event activity classes ˆ Backward and forward near-side correlations of compatible strength LHCb s NN = 5 TeV Activity bin I C ZYAM=1.1 (p+pb) C ZYAM=1.4 (Pb+p) φ 4 φ 1. < p <. GeV/c T Activity bin II C ZYAM=1.3 (p+pb) C ZYAM=1.16 (Pb+p) φ Activity bin III C ZYAM=1.4 (p+pb) C ZYAM=1.7 (Pb+p) φ Activity bin IV C ZYAM=1.51 (p+pb).15 C ZYAM=1.38 (Pb+p) φ arxiv: Activity bin V C ZYAM=1.64 (p+pb) C ZYAM=1.54 (Pb+p) 4 φ Y( φ) CZYAM Y( φ) CZYAM Y( φ) CZYAM Y( φ) CZYAM Y( φ) CZYAM < p < 1. GeV/c 1. < p <. GeV/c. < p < 3. GeV/c T T T C ZYAM=1.61 (p+pb) C ZYAM=.6 (Pb+p)..15 C ZYAM=.83 (p+pb) C ZYAM=4.1 (Pb+p)...15 C ZYAM=3.74 (p+pb) C ZYAM=5.78 (Pb+p) C ZYAM=5.3 (p+pb) C ZYAM=7.81 (Pb+p) C ZYAM=5.67 (p+pb) C ZYAM=8.63 (Pb+p) φ φ φ C ZYAM=.3 (p+pb) C ZYAM=.37 (Pb+p) C ZYAM=.56 (p+pb) C ZYAM=.7 (Pb+p) C ZYAM=.81 (p+pb) C ZYAM=1.14 (Pb+p) C ZYAM=1.19 (p+pb) C ZYAM=1.78 (Pb+p) C ZYAM=1.39 (p+pb) C ZYAM=.7 (Pb+p) φ φ 4 LHCb s NN = 5 TeV p+pb data Pb+p data C ZYAM=.18 (p+pb) C ZYAM=.1 (Pb+p) φ C ZYAM=.3 (p+pb) C ZYAM=.6 (Pb+p) C ZYAM=.9 (p+pb) C ZYAM=.36 (Pb+p) C ZYAM=.3 (p+pb) C ZYAM=.4 (Pb+p) φ φ 4 5 % 3 5% 3% % 3%

28 p-pb - Prompt D nuclear modification factor ˆ D fully reconstructed in the decay D K π +, down to p T = ˆ Minimum bias selections, particle identification and vertex displacement ˆ Prompt yields: D fit to D mass and impact parameter R ppb (p T, y ) = 1 A σppb(p T, y ) σ pp(p T, y ) ˆ σ pp( s = 5TeV): extrapolation using LHCb measurements at 7 and 13 TeV ˆ Analysis of the pp@5tev reference run ongoing ˆ R ppb less than unity at forward rapidities ˆ pqcd calculations that uses EPS9 nuclear PDF parametrization reproduce the data LHCb-CONF-16-3