MulBplicity	  dependence	  of	  Two-­‐parBcle	  correlaBons	  	  in	  p+p	  collisions	  at	  the	  LHC	  with	  ALICE	  JIHYUN	  Bhom	  University	  of	  Tsukuba	  29pHA-­‐6	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  1	  Outline	  •••IntroducBon	  -­‐ALICE	  Two-­‐parBcle	  correlaBons	  -­‐CorrelaBon	  FuncBon	  DeﬁniBon(C2)	  -­‐ObservaBon	  with	  mulBplicity	  dependence	  of	  C2	  -­‐Method	  -­‐Results	  with	  mulBplicity	  dependence	  of	  rescaled-­‐C2	  -­‐Slice	  Δϕ	  projecBon	  of	  rescaled-­‐C2	  	  Conclusion	  	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  2	  MoBvaBon	  	  ALICE	  is	  designed	  to	  study	  heavy-­‐ion	  collisions	  and	  also	  proton-­‐proton	  collisions.	  	  	  	  	  	   	  	  -­‐	  p-­‐p	  collisions	  are	  very	  important	  as	  reference	  for	  RAA	  and	  IAA.	  	  	  	  	  	   	  	  -­‐	  There	  could	  be	  small	  but	  hot	  &	  dense	  maZer	  created	  in	  high-­‐mulBplicity	  p-­‐p	  events	  	  A	  Large	  Ion	  Collider	  Experiment	  	  A Large Ion Collider Experiment
EMCAL
V0 Trigger
Neutralparticles, jets
TRD
Tracking, e-π
separation

T0 Trigger

L3 Magnet

ACORDE
Cosmic trigger
ITS
Tracking, PID

HMPID
PID

DipolemagnetAbsorber

PMD
Photonmultiplicity
PHOS
Photons,
neutral particles
ZDC (at ±115 m w.r.t IP)

TOF
PID
FMD
Forwardmultiplicity

TPC
Tracking,
PID
hZp://aliweb.cern.ch/	  Multiplicity Dependence of 2-Particle Correlations

13/03/29	  JPS	  2013	  in	  HIROSHIMA	  MUON arm
Eva Sicking

33	  Event	  SelecBon	  LHC10c_pass3_	  P+P	  collisions_7.0TeV	  ESD	  TPC	  Event	  cut:	  |Vz|<10cm	  	  Event:	  5M(5,283,589)	  	  MB_trigger	  Main	  track	  cut:	  track	  quality	  cuts(χ2(4),DCA(2cm),#ofcluster/track(70)	  |η|<1.0	  and	  pT	  >0.15GeV/c	  Measured	  number	  of	  track	  distribuBon	  	  pT	  distribuBon	  	  pT	  :	  1	  <pT	  ≤4	  GeV/c	  N_Track	  	  	  	  	  Minimum	  Bias	  	  	  Low_Mt(6)	   	  0<#of	  track≤15	  è	  <#	  of	  track>=6	  Mid_Mt(21)	   15<#of	  track≤30è	  <#	  of	  track>=21	  High_Mt(36)	   30<#of	  track	  	  	  	  	  	  è	  <#	  of	  track>=36	  	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  N	  of	  Event	   	  	  5283589	  	  	  4423097	   14.2-­‐100%	  675847	   1.4-­‐14.2%	  72884	  0-­‐1.4%	  4	  !

CorrelaBon	  FuncBon	  DeﬁniBon(C2)	  ! ∆!, ∆! =!"#$%!
!(∆!, ∆!)!
! !"#$ !(∆!, ∆!)!! (∆!, ∆!) =! ∆!, ∆! =! ∆!, ∆! =! ! ! !"#$!
! !"#$ !∆!"∆!
1!
! !"#$%! !
!

1!
! !"#$% !∆!"∆!

!"#$%(∆!, ∆!) =! !"#$!!
! !"#$ !

!

Event	  1	  !

!

ALICE	  p-­‐p√sNN=7TeV	  Min	  Bias	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  !"#$%

1 ! !
! !"#$% !(∆!, ∆!)!! (∆!, ∆!) = !"#$! ! ∆!, ∆! = ! !"#$% !∆!"∆! !
!
!(∆!, ∆!)!
!

! ! ! !"#$! ∆!, ∆! = !"#$!
!
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! !"#$ !

Event	  2	  ! ! ! !"#$%! ∆!, ∆! = !"#$%!
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!(∆!, ∆!)!! (∆!, ∆!) =!
!(∆!, ∆!)!
!

! ! ! !"#$ !
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! !"#$!"#$%(∆!, ∆!) = !"#$ !! !
!
∆! = ! !"#$ − !!""#$ !
∆! = ! !"#$ − !!""#$ !

φridge:	  	  Resonances,	  string	  fragmentaBon	  Away-­‐side	  jet	  (Δη,	  Δφ)≈(0,π):	  Back-­‐to-­‐back	  jets	  1! ∆!, ∆! =! ! ! !"#$%!
! !"#$% !∆!"∆!
1!"#$%(∆!, ∆!) =Momentum	  conservaBon	  ≈-­‐cos(Δφ)èFlow(v2)	  ! !"#$!!
! !"#$ !

∆! = ! !"#$ − !!""#$ !
∆! = ! !"#$ − !!""#$ !

13/03/29	  Bose-­‐Einstein	  correlaBons	  	  (Δη,	  Δφ)≈(0,0)	  Near-­‐side	  jet	  (Δφ≈0)	  JPS	  2013	  in	  HIROSHIMA	  Δη	  Δφ	  Ridge	  ALICE	  p-­‐p√sNN=7TeV	  Minimum	  Bias	  C2	   5	  0.15<pT,Trig≤1GeV/c	  0.15<pT,Associ≤1GeV/c	  C2(Δη,	  Δφ)	  C2(Δη,	  Δφ)	  C2(Δη,	  Δφ)	  ObservaBon	  with	  mulBplicity	  dependence	  of	  C2	  Δφ	  Δφ	  Δφ	  Δη	  ALICE	  p-­‐p√sNN=7TeV	  C2	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  Δη	  Δη	  Mult.-­‐dependence	  of	  Two-­‐dimensional	  (2-­‐D)	  C2	  charged	  hadrons	  as	  a	  funcBon	  of	  ∆η	  and	  ∆φ	  for	  1<pT,Trig≤4GeV/c,	  1<pT,Associ≤4GeV/c,	  pp	  collisions	  at	  √s	  =	  7	  TeV	  (<#	  of	  Track>=6,	  21,	  36).	  	  	  -­‐	  C2	  shows	  various	  physics	  informaBon	  including	  HBT,	  mini-­‐jet,	  di-­‐jet,	  phi-­‐ridge	  and	  ridge...	  	  -­‐	  The	  shapes	  are	  diﬀerent	  for	  diﬀerent	  mulBplicity	  classes.	  	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  6	  Method	  -­‐To	  normalize	  C2for	  study	  jet	  shape	  	  C2(Δη,	  Δφ)	  1.	  To	  subtract	  uncorrelated	  part.	  	  -­‐Determine	  the	  Minimum.	  	  èC2-­‐Min	  	  Min:	  Average	  of	  minimum	  of	  4	  black	  area,	  	  1.0	  ≤|Δη|≤1.5,	  1.0≤|Δϕ|≤1.5.	  
2.	  To	  scale	  0-­‐1.	  	  Scaling	  factor	  =	  Max	  –	  Min	  	  Max:	  Around	  (0,0),	  Near-­‐side-­‐peak.	  

Δη	  C2(Δη,	  Δφ)	  Sc_C2(Δη,	  Δφ)	  Δφ	  Scaled	  0-­‐1	  ALICE	  p-­‐p√sNN=7TeV	  C2	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  <#	  of	  Track>=36	  13/03/29	  ALICE	  p-­‐p√sNN=7TeV	  Scaled	  C2	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  <#	  of	  Track>=36	  Δφ	  Δη	   2013	  in	  HIROSHIMA	  JPS	  Δφ	  Δη	  7	  Results	  with	  mulBplicity	  dependence	  of	  rescaled-­‐C2	  Δη	  Δφ	  Sc_C2(Δη,	  Δφ)	  Sc_C2(Δη,	  Δφ)	  Sc_C2(Δη,	  Δφ)	  Work	  in	  progress	  Δη	  Δφ	  ALICE	  p-­‐p√sNN=7TeV	  Scaled	  C2	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  Δη	  Δφ	  Mult.-­‐dependence	  of	  2-­‐D	  Scaled	  C2	  charged	  hadrons	  as	  a	  funcBon	  of	  ∆η	  and	  ∆φ	  for	  
1<pT,Trig≤4GeV/c,	  1<pT,Associ≤4GeV/c,	  pp	  collisions	  at	  √s	  =	  7	  TeV	  (<#	  of	  Track>=6,	  21,	  36).	  	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  8	  Results	  with	  mulBplicity	  dependence	  of	  rescaled-­‐C2	  Work	  in	  progress	  Sc_C2(Δη,	  Δφ)	  Sc_C2(Δη,	  Δφ)	  Sc_C2(Δη,	  Δφ)	  ALICE	  p-­‐p√sNN=7TeV	  Scaled	  C2	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  Δφ	  Δη	  Δη	  Δφ	  Δη	  Mult.-­‐dependence	  of	  2-­‐D	  rescaled-­‐C2	  charged	  hadrons	  as	  a	  funcBon	  of	  ∆η	  and	  ∆φ	  for	  
1<pT,Trig≤4GeV/c,	  1<pT,Associ≤4GeV/c,	  pp	  collisions	  at	  √s	  =	  7	  TeV	  with	  jet	  peak	  cut	  oﬀ	  for	  beZer	  demonstraBon	  of	  the	  ridge(<#	  of	  Track>=6,	  21,	  36).	  	  	  -­‐	  Comparison	  between	  3	  mulBplicity	  classes	  are	  done.	  	  -­‐	  High	  mulBplicity	  p-­‐p	  events	  are	  more	  "jet-­‐like".	  	  	  -­‐	  Possible	  indicaBon	  of	  "ridge"	  is	  seen	  at	  high-­‐mulBplicity.	  	  JPS	  2013	  in	  HIROSHIMA	  	   13/03/29	  Δφ	  9	  Slice	  Δφ	  projecBon	  of	  rescaled-­‐C2	  ALICE	  p-­‐p√sNN=7TeV	  Scaled	  C2	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  Work	  in	  progress	  Sc_C2(	  Δφ)	  Low	  mulBplicity	  (6)	  Mid	  mulBplicity	  (21)	  High	  mulBplicity	  (36)	  The	  highest	  Mult.	  Near	  side	  peak	  is	  sharper	  than	  the	  lowest	  Mult.	  jet	  è	  more	  jet-­‐like	  for	  higher	  Mult.	  

Δη	  	  0<|Δη|≤0.2	  Δφ	  Short-­‐range	  slice	  Δφ	  projecBon	  of	  rescaled-­‐C2	  The	  error	  bars	  correspond	  to	  staBsBcal	  errors.	  
13/03/29	  JPS	  2013	  in	  HIROSHIMA	  10	  Slice	  Δφ	  projecBon	  of	  rescaled-­‐C2	  ALICE	  p-­‐p√sNN=7TeV	  Scaled	  C2	  1<pT,Trig≤4GeV/c	  1<pT,Associ≤4GeV/c	  Work	  in	  progress	  RΔφ	  Sc_C2(	  Δφ)	  Δη	  0.7<|Δη|≤2.0	  	  0.2<|Δη|≤2.0	  1.0<|Δη|≤2.0	  1.3<|Δη|≤2.0	  The	  lowest	  Mult.	  of	  scaled	  C2	  is	  concave(Black),	  on	  the	  other	  hand,	  the	  highest	  Mult.	  is	  convex(Red)	  around	  Δφ=0.	  	  è	  Ridge-­‐like	  for	  higher	  Mult.	  

Long	  range	  slice	  Δφ	  projecBon	  of	  resclaedC2	  	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  11	  Conclusion	  1. ALICE	  is	  designed	  to	  study	  heavy-­‐ion	  collisions	  	  and	  also	  proton-­‐proton	  collisions.	  

-­‐p-­‐p	  collisions	  are	  very	  important	  as	  a	  reference	  for	  IAA,	  RAA.	  
-­‐High	  mulBplicity	  p-­‐p	  collisions	  could	  provide	  small	  but	  high	  density	  system.	  

2.	  Mult.-­‐Dep.	  of	  C2	  	  -­‐C2	  shows	  jet-­‐like	  shape	  	  -­‐The	  shapes	  are	  diﬀerent	  for	  diﬀerent	  mulBplicity.	  

3.	  Mult.-­‐Dep.	  of	  rescaled-­‐C2	  	  -­‐Comparison	  with	  3	  mulBplicity	  classes	  is	  done.	  	  -­‐p-­‐p	  events	  are	  more	  jet-­‐like	  for	  high-­‐mulBplicity	  events.	  	  	  	  	  	  	  	  	  -­‐IndicaBon	  of	  ridge-­‐like	  signal	  is	  seen	  for	  high-­‐mulBplicity	  events.	  	  	  	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  12	  • Back	  up	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  13	  Mult.-­‐Dep.	  of	  C2by	  pT_the	  Lowest_Mt(6)	  Associ:	  0.15<pT≤1	  1<pT≤2	  2<pT≤4	  4<pT≤10	  GeV/c	  Trig:	  0.15<pT≤1	  R	  Slice	  Δφ	  projecBon	  of	  C2	  1.3<|Δη|≤2.0	  1<pT≤2	  	  2<pT≤4	  4<pT≤10	  GeV/c	  13/03/29	  JPS	  2013	  in	  HIROSHIMA	  14	  Mult.-­‐Dep.	  of	  C2by	  pT_the	  highest_Mt(36)	  Associ:	  0.15<pT≤1	  1<pT≤2	  2<pT≤4	  4<pT≤10	  GeV/c	  Trig:	  0.15<pT≤1	  Slice	  Δφ	  projecBon	  of	  C2	  1.3<|Δη|≤2.0	  	  1<pT≤2	  2<pT≤4	  4<pT≤10	  GeV/c	  The	  reason	  selected	  pT	  bin	  1<pT≤4	  	  è	  Ridge-­‐like	  for	  higher	  Mult.	  
13/03/29	  JPS	  2013	  in	  HIROSHIMA	  15	  offline includes tracks within | h | < 2.4 (see Section 3 for other offline track selection
system, Ntrk
offline as well as the average of N corrected ,criteria). The table also lists the average values of Ntrktrk
the event multiplicity corrected for all detector and algorithm inefficiencies, as described inSection 5.
(b) CMS MinBias, 1.0GeV/c<p <3.0GeV/c
TTable 1: Number of events for each multiplicity bin used in the 7 TeV analysis with total
offline , wasintegrated luminosity of 980 nb 1 . The multiplicity of offline reconstructed tracks, Ntrk
withinData
the kinematic cuts of |h | < 2.4 and p T > 0.4 GeV/c. The last two columns list
Long-Range Correlationscountedin 7 TeV
offline as well as the average of N corrected , the event multiplicity corrected
the average values of Ntrk
trkfor all detector and algorithm inefficiencies.

ObservaBon	  of	  Long-­‐Range,	  Near-­‐Side	  Angular	  CorrelaBons	  in	  Proton-­‐Proton	  Collisions	  at	  the	  LHC	  (a) CMS MinBias, p >0.1GeV/c
T

R( ∆η,∆φ)R( ∆η,∆φ)720-24∆φ220-2
40

00
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2

4

1 200
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∆η-44-400

20-2-440-2 ∆ηR(∆η,∆φ)R(∆η,∆φ)

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111.7
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↵

2 In this analysis, the so-called CMS highPurity [22] tracks were used. Additionally, a recon--2 ∆η(d) CMS N ≥ 110, 1.0GeV/c<p <3.0GeV/c∆φ2∆φ2corrected
Ntrk

structed track was considered as a primary-track candidate if the significance of the separation

along thebeam axis, z, between the track and the primary vertex, dz /s(dz ), and the significance(d) CMS<3.0GeV/c-4 N ≥ 110, 1.0GeV/c<p(c) CMS N ≥ 110, p >0.1GeV/c

20-2-440-2 ∆η415.9
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96.6
117.8

↵ ⌦(c)-4CMS N ≥ 110, p >0.1GeV/c
TT

0221.43M
19.36M
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302.5k
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3 4Track Selection∆φ2-2 ∆η

∆φ2MinBias
offline12.5-­‐100%	   Ntrk < 35offline
3.1-­‐12.5%	   35  Ntrk < 90
offline < 1101.7-­‐3.1%	   90  Ntrk
offline0-­‐1.7%	  Ntrk
110⌦

R( ∆η,∆φ)∆φ2offline ) Event Count
Multiplicity bin (Ntrk

TR( ∆η,∆φ)R(∆η,∆φ)T

10-1
4(b) CMS MinBias, 1.0GeV/c<p <3.0GeV/cR(∆η,∆φ)(a) CMS MinBias, p >0.1GeV/c420-4

10-1-2 2044-2 ∆η ∆ 2
φ10-1-24T∆φ2Tof the impact
parameter relative to the primary vertex transverse to the beam, dxy /s(dxy ), wereeach less than 3. In order to remove tracks with potentially poorly reconstructed momentumvalues, the relative uncertainty of the momentum measurement, s( p T )/p T , was required to beless than 10%.

To ensure reasonable tracking efficiency and low fake rate, only tracks within |h | < 2.4 andabove a minimum p T value were used. For the inclusive analysis, the selected range was0.1 GeV/c < p T < 5.0 GeV/c. The effect of the upper limit imposed on p T is negligible. Theeffects of the lower p T cut, as well as the effect of the h restriction on the determination ofcluster parameters from Dh correlations, are significant and will be discussed in more detailbelow. To avoid possible bias in the high multiplicity analysis, the lower cutoff was raised top T > 0.4 GeV/c when classifying the event multiplicity in order to match the cut applied in theonline tracking.

2400 2 4 -2 ∆η
4 Calculation of the Two-Particle Correlation Function-400-2 ∆η For both minimum bias and high-multiplicity triggered collision events, the first step in ex-4-4
tracting the correlation function was to divide the sample into bins in track multiplicity. For thebias sample,
10 bins wereused, each containing about the same number of events.
Figure 7: 2-D two-particle correlation functions for 7 TeV pp (a) minimum
minimum
bias eventswithFollowing an approach similar to that in Refs. [3, 6], the p T -inclusive charged two-particle cor: 2-D two-particle
functions bias
for 7events
TeV pp(a)1minimum
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eventspT <GeV/c,(c) high multiplicity
S N (Dh, Df)(Ntrk110)bias
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cut off in order to< p T < 3 GeV/c. The sharp near-side peak from jet correlations is cut off in order tobetter illustrate the structure outside that region.
ustrate the structure outside that region.
arXiv:1009.4122v1	  [hep-­‐ex]	  21	  Sep	  2010	  of particles
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