Quarkonium results in pp collisions from ALICE...ATLAS and CMS measurements at y=0 Quarkonia in...

Quarkonium results in pp collisions from ALICE

Giuseppe E Bruno Università di Bari and INFN – Italy

for the ALICE collaboration

Quarkonia in Deconfined Matter

Acitrezza September 28-30 2011

Outline:   introduction   measurements in pp at √s=7 and 2.76 TeV

  Integrated and differential cross sections for inclusive production

  Multiplicity dependence at √s = 7 TeV   J/ψ from B decays at √s = 7 TeV

  outlook   J/ψ polarisation and Upsilon measurements at

√s = 7 TeV

Introduction   do I need to motivate the study of quarkonia within this

audience?   J/ψ is “puzzling” in PbPb …

  … and in fact we are at work at this meeting   but J/ψ production is not that obvious in p-p collisions too

  the production mechanisms in p-p collisions are not fully understood

  but recent theoretical developments can account for the yields

Quarkonia in deconfined matter Giuseppe E. Bruno 2

J.P.Lansberg, PoS(ICHEP 2010), 206

Introduction

  theoretical uncertainties are big   NNLO* corrections in the CSM model give a good

description of the pt spectrum at intermediate pt.   more observables from experiment should be

employed to constrain theory? Quarkonia in deconfined matter Giuseppe E. Bruno 3

S.J.Brodsky, J.P.Lansberg, PRD81 (2010) 051502

Introduction

Experimentally accessible information   production rates (cross-sections)

  inclusive and exclusive channels: direct, feed-down from beauty and higher charmonium states

 differential vs. rapidity, transverse momentum

 correlations   J/ψ correlations with hadrons, leptons,

photons  understand the production context

  event multiplicity   underlying event, jet fragmentation cone

 polarization measurements Quarkonia in deconfined matter Giuseppe E. Bruno 4

Quarkonia with ALICE

 Quarkonia can be measured in two ways:   in the central barrel in the e+e- channel (|y|<0.9)   in the forward spectrometer in the µ+µ- channel

(2.5<y<4) Quarkonia in deconfined matter Giuseppe E. Bruno 5

e+ e- µ+

µ-

Quarkonia at central rapidity


ICPAQGP Goa 2010 J. Schukraft PLC 20J. Schukraft

ITS

TPC

TRD

TOF

EMCAL

PHOS

HMPID

L3 Magnet

Key detectors:   tracking

  TPC,ITS   PID

  TPC, TOF, TRD, EMCAL

  vertexing   ITS

  trigger   EMCAL, TRD

0<φ<2π |ηe| < 0.9

e+ e-

Quarkonia at central rapidity


ICPAQGP Goa 2010 J. Schukraft PLC 20J. Schukraft

  tracking   PID

K. Aamodt et al. (ALICE Collaboration), Phys. Lett. B in press, arXiv:1105.0380

Quarkonia at forward rapidity

  coverage: -4.0<η<-2.5 and pµ>4.0 GeV/c   dipole magnet and 5 tracking chambers used for momentum

measurement   muons are isolated using hadron absorbers   it can run at higher luminosities compared to the slower

central rapidity detectors   allows measurement of heavy quarkonia (J/ψ, ψ', Υ family)


0<φ<2π -4.0<ηµ<-2.5 pµ > 4 GeV/c

SPD

V0-A

V0-C

Event selection and data sample   Triggers:

  Minimum bias (MB) based on interaction trigger:   SPD(pixels) or V0-A(scintillators) or V0-C(scintillators)   At least one charged particle in 8 η units   87% efficient on σinel

  Single muon trigger (pTthr=0.5 GeV/c):

  Forward Muon in coincidence with MB   read out MUON, SPD, ZDC, V0, FMD

  Results presented today based on:

  2010 pp run at 7 TeV   2011 pp run at 2.76 TeV


Energy J/ψ→µ+µ- J/ψ→e+e-

7.0 TeV 15.6 nb-1 5.6 nb-1

2.76 TeV 20.2 nb-1 1.1 nb-1

Kinematical and track quality cuts

J/ψ → e+ + e-

  |ηe| < 0.9   pT

e> 1.0 GeV/c   |yJ/ψ|<0.9   high quality ITS+TPC

tracks   electron PID based on

TPC's dE/dx   rejection of e from γ

conversions


J/ψ → µ+ + µ-   pµ> 4.0 GeV/c   2.5<yJ/ψ<4.0   one muon trigger

matching   17.6<Rabs<89 cm

(radial track position at the end of the absorber)

Efficiency times acceptance


Acc

epta

nce

x ef

ficie

ncy

<Axε>=10%

<Axε>=33%

J/ψ → e+e- at 7 TeV, |y| < 0.9 J/ψ → µ+µ- at 2.76 TeV, 2.5<y <4

ALICE unique measurement at LHC

Signal extraction (7 TeV)


2C

ount

s pe

r 40

MeV

/c

20406080

100120140160180 OS

LS*1.23TrkRot

=7 TeVsALICE pp

)2 (GeV/ceem1.5 2 2.5 3 3.5 4 4.5 5

-200

20406080

100120140

OS-1.23*LS/dof=1.2)2MC (

Lint=5.6 nb-1 NJ/ψ=352±32 S/B=1.2 S/√(S+B)=14

  signal extracted using bin counting, after bkg. subtraction

  MC simulations describes well the signal shape

  Fit with Crystall-Ball functions (J/ψ and ψ’) plus double exponential (bkg.) describes well the dimuon invariant mass spectra

Lint=7.9 nb-1 NJ/ψ=957±56 S/B≃2.6 mJ/ψ=3.118±0.005 GeV/c2

σJ /ψ=94±8 MeV/c2

K. Aamodt et al. (ALICE Collaboration), Phys. Lett. B in press, arXiv:1105.0380

Signal extraction (2.76 TeV)


Lint=1.1 nb-1 NJ/ψ=41±9

  signal extracted using bin counting, after bkg. subtraction

  MC simulations describes well the signal shape

  Fit with Crystall-Ball functions (J/ψ and ψ’) plus double exponential (bkg.) describes well the dimuon invariant mass spectra

NJ/ψ=1287±48

Systematic uncertainties at √s=7 TeV

  systematic error due to the unknown polarization estimated for extreme scenarios

  major systematic errors come from signal extraction and reconstruction efficiency (for the di-electron channel)

  similar uncertainties at √s=2.76 TeV Quarkonia in deconfined matter Giuseppe E. Bruno 14

e+e- µ+µ-

Signal extraction 8.5% 7.5%

Acceptance input 1.5% 5%

Trigger efficiency 0 4%

Reconstruction efficiency 11% 3%

Trigger enhancement - 3%

Luminosity 4% 5.5%

B.R. 1%

Polarization λ=-1 λ=1 λ=-1 λ=1

Collins-Soper +19% -13% +31% -15%

Helicity +21% -15% +22% -10%

Rapidity dependence of the inclusive cross-section

  Cross section determination from van der Meer scan:

7 TeV σMB= 62.3±4.3 mb 2.76 TeV σMB= 54.2±3.8 mb

  systematic uncertainties from

beam intensities (~4%)


d! (pp! J /" + X)dy

=NJ /"

corr

"y BR(J /"! l+l# )!MB

NMB

! J /" (| y |< 0.9) =10.7±1.0(stat)±1.6(syst)!2.3+1.6(syst pol) µb

! J /" (2.5< y < 4) = 6.31± 0.25(stat)± 0.76(syst)!1.96+0.95(syst pol) µb

7 TeV ALICE coll., PLB in press arXiv:1105.0380 (2011)

! J /" (| y |< 0.9) = 6.44±1.42(stat)± 0.88(syst)± 0.52(lumi)!1.42+0.64(syst pol) µb

! J /" (2.5< y < 4) = 3.46± 0.13(stat)± 0.32(syst)± 0.28(lumi)!1.11+0.55(syst pol) µb

2.76 TeV ALICE preliminary

K. Oyama et al. (ALICE Collaboration) arXiv:1107.0692

Rapidity dependence of the inclusive cross-section


  Error bars are statistical and systematic errors (added in quadrature), excluding luminosity and polarization

  Boxes are correlated error bars from luminosity

  Comparison to CMS and LHCb shows agreement within error bars

ALICE: Phys. Lett. B in press ATLAS: Nucl. Phys. B850 (2011) 387 CMS Phys. J. C71, (2011) 1575 LHCb Eur. Phys. J. C71 (2011) 1645

y-5 -4 -3 -2 -1 0 1 2 3 4 5

b)µ

/dy

(J/

d0

1

2

3

4

5

6

7

8

9

10-e+ALICE, e-µ+µALICE,

CMSLHCb

open: reflected

=7 TeVspp

pT dependence of the inclusive cross-section


  Error bars are statistical and systematic errors (added in quadrature), excluding luminosity and polarization

  Boxes are correlated error bars from luminosity

  Good agreement between ALICE and LHCb for 2.5<y<4.0

  At mid-rapidity, ALICE and CMS+ATLAS cover the full pt range

ALICE: Phys. Lett. B in press ATLAS: Nucl. Phys. B850 (2011) 387 CMS Phys. J. C71, (2011) 1575 LHCb Eur. Phys. J. C71 (2011) 1645

(GeV/c)T

p0 2 4 6 8 10 12

b/G

eV/c

)µ

dy (

T /d

pJ/

2 d

-210

-110

1

, |y|<0.9-e+ALICE e, 2.5<y<4.0-µ+µALICE

CMS, |y|<1.2ATLAS, |y|<0.75LHCb, 2.5<y<4.0

=7 TeVspp

Comparisons to theoretical predictions


  CS LO for direct J/ψ production reproduces rapidity dependence, despite large uncertainties

  Inclusive J/ψ production at LHC energies, at low pT: J/ψ feed-down from higher charmonium states χc and ψ’ ~ 40% J/ψ from B-hadrons ~ 10% direct J/ψ ~ 50%

  CS+CO NLO (NRQCD) reproduces well the spectra for pT > 3 GeV/c

Energy dependence

  line = NLO cross section calculation for ccbar scaled to CDF data


CDF Collaboration PRD71 (2005) 032001 PHENIX Collaboration, PRL 98 (2007) 232002 M.Mangano et al., Nucl.Phys.B373 (1992) 295

  J/ψ mean pT grows roughly as ln(s1/2)

Multiplicity dependence   Charged particle multiplicity (dNch/dηmax ~30) reached in pp at 7 TeV is

comparable with semi-central CuCu collisions (50-55%) @ 200 GeV → “heavy-ion like” effects in p-p collisions at high multiplicity at LHC?


  Almost linear increase of J/ψ yield with charged particle multiplicity   Multi-parton interactions?   Contributions from higher order

pQCD diagrams?

  Different increase with respect to high pT muons (~80% from heavy flavour decays at 4 <pT< 8 GeV/c)

Prompt J/ψ and J/ψ from B hadrons

  Component of J/ψ from B hadrons can be measured thanks to the excellent vertexing capabilities of the ITS

  technique:   simultaneous likelihood fit of invariant mass and

pseudo-proper decay length lJ/ψ


)/(/

/ ψψ

ψ JpmLlT

JxyJ ×=

)(sec ϕrrrL primxy

−=

|yJ/ψ|<0.9

Fraction of J/ψ from B

  lowest pT at central rapidity at LHC energies

  nicely complement the ATLAS and CMS measurements at y=0


Prompt and non-prompt J/ψ cross section, pt>2 GeV/c

  inclusive cross-section, pt>2 GeV/c:

  fraction of J/ψ from B hadrons:


d! inclusive pTJ /" > 2GeV / c, | yJ /" |< 0.9( )

dy= 3.76± 0.37(stat)± 0.49(syst)!0.59

+0.79(pol.) µb

±4%(lumi)

FB pTJ /! > 2GeV / c, | yJ /! |< 0.9( ) = 0.150± 0.059± 0.026(syst)+0.043(!HE=+1)!0.022(!CS=!1)

d! prompt pTJ /" > 2GeV c, | yJ /" |< 0.9( )

dy= 3.20± 0.38(stat)± 0.43(syst)

!0.58(!HE

= +1) + 0.82(!HE

= !1)

!0.29(!CS

= +1) + 0.53(!CS

= !1) µb

  prompt cross-section, pt>2 GeV/c:

±4%(lumi)

Outlook: J/ψ polarisation (2.5<y<4)

  key observable to study the production mechanism

  determination of the full angular dependence of J/ψ (λθ, λφ, λθφ) is ongoing

  preliminary results soon:   expected error

on λθ ~ 0.15 for 3<pT<8 GeV/c


Outlook: upsilon family and more

  2011 data will allow the measurement of Υ in the di-muon channel   upsilon data now “on tape”

and results will be available soon

  2011 and beyond:   extension of PID and trigger

to EMCAL and TRD   Υ family measurements at

both rapidities; J/ψ-hadron correlations and radiative decay from higher charmonium states (χc and ψ’) at mid-rapidity.


Conclusions J/ψ production in p+p collisions at √s = 2.76 and 7 TeV:

  integrated and differential cross sections for inclusive production were presented. Results have been compared to other experiments, as well as to theoretical models on quarkonia production

  results at 2.76 TeV serve also as reference to our PbPb measurements

  linear dependence on charged particle multiplicity was observed

  the fraction of J/ψ from B decays was measured at mid-rapidity

  polarization analysis almost ready, results soon

  upsilon measurement with 2011 data coming


Afterword


  you may wonder what is the picture in my first slide

J/ψ ψ’

Υ

Minv(l+,l-)

dN/dM

Afterword


from the movie “La terra trema” by Luchino Visconti, based on the novel by Giovanni Verga “I Malavoglia” set in Acitrezza

Afterword


  thanks for your patience

J/ψ ψ’

Υ

Minv(l+,l-)

dN/dM

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