Nicol o Jacazio for the ALICE collaboration University of Turin and … · 2018. 11. 16. · Nicol...
1
Transverse momentum spectra of π , K and p in small collision systems: search for collective phenomena Nicol`o Jacazio for the ALICE collaboration University of Turin and INFN The ALICE detector I VZERO detectors trigger and centrality/multiplicity Main detectors for PID: I Inner tracking system (ITS) I Time projection chamber (TPC) I Time of flight (TOF) I High momentum PID (HMPID) Measuring the event multiplicity VZERO percentiles Event multiplicity at forward-rapidity obtained measuring the signal in the two V0 detectors and dividing its distribution into percentile-based classes Counting tracks Event multiplicity at mid-rapidity (|η | < 0.8) obtained by counting tracks reconstructed in the barrel detectors and segments of tracks reconstructed with the SPD detector to increase the acceptance VZERO Amplitude (a.u.) 0 5000 10000 15000 20000 Events -2 10 -1 10 1 10 2 10 Data Glauber fit 0-5% 5-10% 10-20% 20-30% 30-40% 40-50% 50-60% 0 500 1000 10 2 10 70-80% 60-70% ALI-PUB-8808 [2] VZERO-A amplitude (a.u.) 0 100 200 300 400 500 600 700 800 900 Events (a.u.) 1 10 2 10 3 10 4 10 0-5% 5-10% 10-20% 20-40% 40-60% 60-80% 80-100% = 5.02 TeV NN s ALICE p-Pb at 0-5% 5-10% 10-20% 20-40% 40-60% 60-80% 80-100% 03/05/2013 ALI-PERF-51387 ch N 0 10 20 30 40 50 60 70 ) ch N P( -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 1 ALICE pp > 0.15 GeV T p | < 0.8, η > 0, | ch N = 7 TeV, s ALI-PUB-59106 [3] PID strategies ITS ) c (GeV/ p 0.07 0.1 0.2 0.3 0.4 0.5 1 2 3 4 5 m) μ (keV/300 x /d E ITS d 0 100 200 300 400 500 600 700 05/03/2013 TeV 5.02 = NN s p-Pb π e K p ALI-PERF-46922 I Specific energy-loss in the ITS vs momentum I dE /dx resolution for the ITS ∼ 10% (p–Pb) TPC ) c (GeV/ p 0.2 0.3 0.4 1 2 3 4 5 6 7 8 9 10 (arb. units) x /d E TPC d 0 100 200 300 400 500 600 700 π e K p d t 05/03/2013 TeV 5.02 = NN s p-Pb ALI-PERF-46927 I Specific energy-loss in the TPC vs momentum I dE/dx resolution for the TPC ∼ 5% (p–Pb) TOF p-Pb minimum bias p K π p K π = 5.02 TeV NN s p-Pb 5/03/2013 (GeV/c) p 0 1 2 3 4 5 β TOF 0.2 0.4 0.6 0.8 1 = 5.02 TeV NN s p-Pb 5/03/2013 π K p K p ALI-PERF-46936 I Particle velocity β measured by TOF vs momentum I TOF time resolution ∼ 85 - 120 ps depending on multiplicity (p–Pb) HMPID ) c p (GeV/ 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 HMPID Cherenkov angle (rad) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 π K p TeV 7 = s pp ALI-PUB-72451 [5] I Mean Cherenkov angle vs momentum I 3σ separation for π -K for p T < 3 GeV /c I 3σ separation for p-K for p T < 5 GeV /c Results Spectra in pp The multiplicity in pp can be quantified by the ratio: z raw = (N raw ch ) limit h N raw ch i mult>0 hN raw ch i =9.6, |η | < 0.8 N raw ch z raw 7-12 0.7-1.3 13-19 1.4-2.0 20-28 2.1-2.9 29-39 3.0-4.1 40-49 4.2-5.1 50-59 5.2-6.2 60-71 6.3-7.4 72-82 7.5-8.6 I Multiplicity dependence of the spectral shape I Spectra become progressively harder as a function of multiplicity and particle mass → Mass ordering as expected from hydrodynamics -1 ) c ) (GeV/ T p d y /(d N 2 d ev N 1/ -2 10 -1 10 1 10 raw z mult > 0 [0.7-1.4) [1.4-2.1) [2.1-3.0) [3.0-4.2) [4.2-5.2) [5.2-6.3) [6.3-7.5) [7.5-8.6] + π = 7 TeV s pp -1 10 1 Uncertainty statistical total systematic mult. related syst. + K -2 10 -1 10 p ALICE Preliminary ) c (GeV/ T p 0.5 1 1.5 2 2.5 ratio to mult. > 0 1 10 ) c (GeV/ T p 0.2 0.4 0.6 0.8 1 1.2 1.4 1 10 ) c (GeV/ T p 0.5 1 1.5 2 2.5 1 10 ALI-PREL-81642 The Blast-Wave fits The blast-wave model is a simplified hydro model with the following functional form: E d 3 N dp 3 ∼ f (p t )= R R 0 m T K 1 (m T cosh ρ/T fo ) I 0 (p T sinh ρ) rdr m T = p m 2 + p 2 T β r (r )= β s (r/R) n ρ = tanh -1 β r 0 1 2 3 4 5 6 ] -2 ) c ) [(GeV/ y d T p /(d N 2 d T p π 1/2 ev N 1/ -5 10 -4 10 -3 10 -2 10 -1 10 1 10 2 10 3 10 4 10 5 10 = 2.76 TeV NN s ALICE, Pb-Pb, PRC 88, 044909 (2013) Centrality Class: 0-5% (100x) - π + + π (10x) - + K + K (1x) p p + Blast-Wave global fit range c : 0.5-1.0 GeV/ π c K: 0.2-1.5 GeV/ c p: 0.3-3.0 GeV/ ) c (GeV/ T p 0 1 2 3 4 5 6 data / model 1 1.5 - π + + π 1 1.5 - + K + K 1 1.5 p p + ALI-DER-67916 [4] 0 1 2 3 4 5 6 ] -2 ) c ) [(GeV/ y d T p /(d N 2 d T p π 1/2 ev N 1/ -5 10 -4 10 -3 10 -2 10 -1 10 1 10 2 10 3 10 4 10 = 5.02 TeV NN s ALICE, p-Pb, PLB 728 (2014) 25-38 V0A Multiplicity Class (Pb-side): 0-5% (100x) - π + + π (10x) - + K + K (1x) p p + Blast-Wave global fit range c : 0.5-1.0 GeV/ π c K: 0.2-1.5 GeV/ c p: 0.3-3.0 GeV/ ) c (GeV/ T p 0 1 2 3 4 5 6 data / model 1 1.5 - π + + π 1 1.5 - + K + K 1 1.5 p p + ALI-DER-67956 [1] 0 1 2 3 4 5 6 ] -2 ) c ) [(GeV/ y d T p /(d N 2 d T p π 1/2 ev N 1/ -4 10 -3 10 -2 10 -1 10 1 10 2 10 3 10 = 7 TeV s ALICE, pp, ALICE Preliminary Multiplicity Class: [0.7, 1.4) raw z (100x) + π (10x) + K p (1x) Blast-Wave global fit range c : 0.5-1.0 GeV/ π c K: 0.3-1.5 GeV/ c p: 0.5-2.5 GeV/ ) c (GeV/ T p 0 1 2 3 4 5 6 data / model 1 1.5 + π 1 1.5 + K 1 1.5 p ALI-PREL-72482 References 1. B.Abelev et Al. (ALICE Coll.) Phys. Lett. B728 (2014) 25-38 2. K. Aamodt et Al. (ALICE Coll.) Phys. Rev. Lett. 106 (2011), 032301 3. ALICE-PUBLIC-2013-001 4. B.Abelev et Al. (ALICE Coll.) Phys. Rev. C 88, 044910 (2013) 5. ALICE Coll. arXiv:1402.4476 [nucl-ex] 6. E. Schnedermann, J. Sollfrank, and U. Heinz Phys. Rev. C 48, 2462 (1993) Spectra in p–Pb ) c (GeV/ T p 0 1 2 3 4 5 ] -2 ) c ) [(GeV/ y d T p /(d N 2 ) d T p π 1/(2 ev N 1/ -4 10 -3 10 -2 10 -1 10 1 10 2 10 3 10 4 10 - π + + π = 5.02 TeV NN s ALICE, p-Pb, < 0.5 CMS y 0 < V0A Multiplicity Classes (Pb-side) 0-5% (64x) 5-10% (32x) 10-20% (16x) 20-40% (8x) 40-60% (4x) 60-80% (2x) 80-100% (1x) individual fit ALI-PUB-58037 [1] ) c (GeV/ T p 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 ] -2 ) c ) [(GeV/ y d T p /(d N 2 ) d T p π 1/(2 ev N 1/ -4 10 -3 10 -2 10 -1 10 1 10 2 10 - + K + K = 5.02 TeV NN s ALICE, p-Pb, < 0.5 CMS y 0 < V0A Multiplicity Classes (Pb-side) 0-5% (64x) 5-10% (32x) 10-20% (16x) 20-40% (8x) 40-60% (4x) 60-80% (2x) 80-100% (1x) individual fit ALI-PUB-58041 [1] ) c (GeV/ T p 0 1 2 3 4 5 6 7 ] -2 ) c ) [(GeV/ y d T p /(d N 2 ) d T p π 1/(2 ev N 1/ -5 10 -4 10 -3 10 -2 10 -1 10 1 10 p p + = 5.02 TeV NN s ALICE, p-Pb, < 0.5 CMS y 0 < V0A Multiplicity Classes (Pb-side) 0-5% (64x) 5-10% (32x) 10-20% (16x) 20-40% (8x) 40-60% (4x) 60-80% (2x) 80-100% (1x) individual fit ALI-PUB-58045 [1] Spectra evolution with multiplicity in p–Pb: shown to exhibit behaviour that is qualitatively similar to both pp and Pb–Pb Particle ratios ) c (GeV/ T p 0 0.5 1 1.5 2 2.5 3 Ratio 0.5 1 1.5 2 2.5 3 3.5 ) c (GeV/ T p 0 0.5 1 1.5 2 2.5 3 Ratio 0.5 1 1.5 2 2.5 3 3.5 ALICE Preliminary 2 +syst 2 stat uncert.= = 2.76 TeV NN s Pb-Pb, >=13.4 η /d ch N >=1601/<d η /d ch N <d = 5.02 TeV NN s p-Pb, >=9.8 η /d ch N >=45/<d η /d ch N <d = 7 TeV s pp, <1.4) raw z ≤ 8.6)/(0.7 ≤ raw z ≤ (7.5 ALI-PREL-81606 (p/π ) high multiplicity / (p/π ) low multiplicity I Heavier particles have larger p T for all the colliding systems I Same trend for pp and p–Pb I Higher increase in Pb–Pb Results from BW fits > T β < 0.3 0.4 0.5 0.6 0.7 n 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 > T β < 0.3 0.4 0.5 0.6 0.7 n 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ALICE Preliminary Uncertainties: syst.(from global fit of data) Fit-range related syst. uncert.- not included = 7 TeV s pp, = 5.02 TeV NN s p-Pb, = 2.76 TeV NN s Pb-Pb, ALI-PREL-81587 (GeV) kin T 0.08 0.1 0.12 0.14 0.16 0.18 0.2 n 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 (GeV) kin T 0.08 0.1 0.12 0.14 0.16 0.18 0.2 n 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ALICE Preliminary Uncertainties: syst.(from global fit of data) Fit-range related syst. uncert.- not included = 7 TeV s pp, = 5.02 TeV NN s p-Pb, = 2.76 TeV NN s Pb-Pb, ALI-PREL-81583 〉 T β 〈 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 (GeV) kin T 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 = 5.02 TeV NN s ALICE, p-Pb, V0A Multiplicity Classes (Pb-side) = 2.76 TeV NN s ALICE, Pb-Pb, = 7 TeV s ALICE, pp, = 7 TeV (with Color Reconnection) s PYTHIA8, = 7 TeV (without Color Reconnection) s PYTHIA8, ALI-DER-58133 I n -hβ t i correlations, similar for pp, p–Pb and Pb–Pb I Higher multiplicity at higher hβ t i I n - T kin correlations, similar for pp and p–Pb. Pb–Pb has lower values I Higher multiplicity at lower T kin I Similar trends in pp and p–Pb I PYTHIA with CR reproduces the trend I Higher multiplicity at higher hβ t i Summary and conclusions I π , K and p spectra measured in pp collisions at 7 TeV and p–Pb collisions at 5.02 TeV are presented I The comparison of pp, p–Pb and Pb–Pb shows similarities for the three systems as a function of multiplicity I Similar trends are observed for the three colliding systems and hint at collective effects in p–Pb and pp I Serves as input for further theoretical investigation of the phenomena seen at the LHC
Transcript of Nicol o Jacazio for the ALICE collaboration University of Turin and … · 2018. 11. 16. · Nicol...
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Transverse momentum spectra of π, K and p in small collision systems:search for collective phenomena
Nicolò Jacazio for the ALICE collaborationUniversity of Turin and INFN
The ALICE detectorI VZERO detectors
trigger and
centrality/multiplicity
Main detectors for PID:
I Inner tracking system (ITS) I Time projection chamber (TPC)
I Time of flight (TOF) I High momentum PID (HMPID)
Measuring the event multiplicityVZERO percentiles
Event multiplicity at forward-rapidity obtained measuring the signal in the
two V0 detectors and dividing its distribution into percentile-based classes
Counting tracksEvent multiplicity at mid-rapidity (|η| < 0.8) obtained by counting tracksreconstructed in the barrel detectors and segments of tracks reconstructed
with the SPD detector to increase the acceptance
VZERO Amplitude (a.u.)0 5000 10000 15000 20000
Ev
en
ts
-210
-110
1
10
210
Data
Glauber fit
0-5
%
5-1
0%
10
-20
%
20
-30
%
30
-40
%
40
-50
%
50
-60
%
0 500 1000
10
210
70
-80
%
60
-70
%
ALI−PUB−8808 [2]
VZERO-A amplitude (a.u.)0 100 200 300 400 500 600 700 800 900
Events
(a.u
.)
1
10
210
310
410
0-5%
5-10%
10-20%
20-40%
40-60%
60-80%
80-100%
= 5.02 TeVNN
sALICE p-Pb at 0-5%5-10%10-20%20-40%40-60%60-80%80-100%
03/05/2013
ALI−PERF−51387
chN0 10 20 30 40 50 60 70
)ch
NP
(
-710
-610
-510
-410
-310
-210
-110
1
ALICE pp
> 0.15 GeVT
p| < 0.8, η > 0, |chN = 7 TeV, s
ALI−PUB−59106 [3]
PID strategiesITS
)c (GeV/p
0.07 0.1 0.2 0.3 0.4 0.5 1 2 3 4 5
m)
µ (
ke
V/3
00
x/d
EIT
S d
0
100
200
300
400
500
600
700
05/03/2013
TeV 5.02 = NN
sp-Pb
π
e
K p
ALI−PERF−46922
I Specific energy-loss in the ITS vs momentumI dE/dx resolution for the ITS ∼ 10% (p–Pb)
TPC
)c (GeV/p
0.2 0.3 0.4 1 2 3 4 5 6 7 8 910
(arb
. u
nits)
x/d
ET
PC
d
0
100
200
300
400
500
600
700
π
e
K
p d t
05/03/2013
TeV 5.02 = NNsp-Pb
ALI−PERF−46927
I Specific energy-loss in the TPC vs momentumI dE/dx resolution for the TPC ∼ 5% (p–Pb)
TOF
p-Pb minimum bias
p
K
π
p
K
π
= 5.02 TeVNN
sp-Pb
5/03/2013
(GeV/c)p0 1 2 3 4 5
βT
OF
0.2
0.4
0.6
0.8
1
= 5.02 TeVNN
sp-Pb
5/03/2013
π
K
p
K
p
ALI−PERF−46936
I Particle velocity β measured by TOF vsmomentum
I TOF time resolution ∼ 85− 120 ps depending
on multiplicity (p–Pb)
HMPID
)cp (GeV/0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
HM
PID
Chere
nkov a
ngle
(ra
d)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
π
K
p
TeV 7 = spp
ALI−PUB−72451 [5]
I Mean Cherenkov angle vs momentumI 3σ separation for π-K for pT < 3 GeV/c
I 3σ separation for p-K for pT < 5 GeV/c
ResultsSpectra in pp
The multiplicity in pp can
be quantified by the ratio:
zraw =(N rawch )limit〈N rawch 〉mult>0
〈N rawch 〉 = 9.6, |η| < 0.8
N rawch zraw
7-12 0.7-1.313-19 1.4-2.020-28 2.1-2.929-39 3.0-4.140-49 4.2-5.150-59 5.2-6.260-71 6.3-7.472-82 7.5-8.6
I Multiplicity dependenceof the spectral shape
I Spectra becomeprogressively harder as a
function of multiplicity
and particle mass
→ Mass ordering asexpected from
hydrodynamics
-1 )c
) (G
eV
/T
pd
y/(
dN
2 d
ev
N1/
-210
-110
1
10
rawz
mult > 0
[0.7-1.4)
[1.4-2.1)
[2.1-3.0)
[3.0-4.2)
[4.2-5.2)
[5.2-6.3)
[6.3-7.5)
[7.5-8.6]
+π
= 7 TeVspp -110
1
Uncertainty
statistical
total systematic
mult. related syst.
+K-210
-110
p
ALICE Preliminary
)c(GeV/T
p
0.5 1 1.5 2 2.5
ratio to m
ult. >
0
1
10
)c(GeV/T
p
0.2 0.4 0.6 0.8 1 1.2 1.4
1
10
)c(GeV/T
p
0.5 1 1.5 2 2.5
1
10
ALI−PREL−81642
The Blast-Wave fitsThe blast-wave model is a simplified hydro model with the following functional form:
E d3Ndp3 ∼ f (pt) =
∫ R0 mTK1 (mT cosh ρ/Tfo) I0 (pT sinh ρ) rdr
mT =√m2 + p2T βr (r) = βs (r/R)
n ρ = tanh−1βr
0 1 2 3 4 5 6
]-2 )
c)
[(G
eV
/y
dT
p/(
dN
2 d
Tp
π 1
/2e
vN
1/ -510
-410
-310
-210
-110
1
10
210
310
410
510 = 2.76 TeV
NNsALICE, Pb-Pb,
PRC 88, 044909 (2013)Centrality Class: 0-5%
(100x)-π + +π
(10x)-
+ K+K
(1x)pp +
Blast-Wave
global fit range
c: 0.5-1.0 GeV/π
cK: 0.2-1.5 GeV/
cp: 0.3-3.0 GeV/
)c (GeV/T
p
0 1 2 3 4 5 6
data
/ m
odel
1
1.5 -π + +π
1
1.5-
+ K+
K
1
1.5 pp +
ALI−DER−67916 [4]
0 1 2 3 4 5 6
]-2 )
c)
[(G
eV
/y
dT
p/(
dN
2 d
Tp
π 1
/2e
vN
1/ -510
-410
-310
-210
-110
1
10
210
310
410 = 5.02 TeVNN
sALICE, p-Pb,
PLB 728 (2014) 25-38V0A Multiplicity Class (Pb-side): 0-5%
(100x)-π + +π
(10x)-
+ K+K
(1x)pp +
Blast-Wave
global fit range
c: 0.5-1.0 GeV/π
cK: 0.2-1.5 GeV/
cp: 0.3-3.0 GeV/
)c (GeV/T
p
0 1 2 3 4 5 6
data
/ m
odel
1
1.5 -π + +π
1
1.5-
+ K+
K
1
1.5 pp +
ALI−DER−67956 [1]
0 1 2 3 4 5 6
]-2 )
c)
[(G
eV
/y
dT
p/(
dN
2 d
Tp
π 1
/2e
vN
1/
-410
-310
-210
-110
1
10
210
310
= 7 TeVsALICE, pp,
ALICE Preliminary Multiplicity Class: [0.7, 1.4)rawz
(100x)+π
(10x)+K
p (1x)
Blast-Wave
global fit range
c: 0.5-1.0 GeV/π
cK: 0.3-1.5 GeV/
cp: 0.5-2.5 GeV/
)c (GeV/T
p
0 1 2 3 4 5 6
data
/ m
odel
1
1.5 +π
1
1.5 +K
1
1.5 p
ALI−PREL−72482
References
1. B.Abelev et Al. (ALICE Coll.) Phys. Lett. B728 (2014) 25-38
2. K. Aamodt et Al. (ALICE Coll.) Phys. Rev. Lett. 106 (2011), 032301
3. ALICE-PUBLIC-2013-001
4. B.Abelev et Al. (ALICE Coll.) Phys. Rev. C 88, 044910 (2013)
5. ALICE Coll. arXiv:1402.4476 [nucl-ex]
6. E. Schnedermann, J. Sollfrank, and U. Heinz Phys. Rev. C 48, 2462 (1993)
Spectra in p–Pb
)c (GeV/T
p
0 1 2 3 4 5
]
-2 )c
) [(
GeV
/y
dT
p/(
dN
2)
dT
pπ
1/(
2e
vN
1/
-410
-310
-210
-110
1
10
210
310
410
-
π + +
π
= 5.02 TeVNNsALICE, p-Pb,
< 0.5CMS
y0 <
V0A Multiplicity Classes(Pb-side)
0-5% (64x)
5-10% (32x)
10-20% (16x)
20-40% (8x)
40-60% (4x)
60-80% (2x)
80-100% (1x)
individual fit
ALI−PUB−58037 [1] )c (GeV/Tp0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
]
-2 )c
) [(
GeV
/y
dT
p/(
dN
2)
dT
pπ
1/(
2e
vN
1/
-410
-310
-210
-110
1
10
210
- + K
+K
= 5.02 TeVNNsALICE, p-Pb,
< 0.5CMS
y0 <
V0A Multiplicity Classes(Pb-side)
0-5% (64x)
5-10% (32x)
10-20% (16x)
20-40% (8x)
40-60% (4x)
60-80% (2x)
80-100% (1x)
individual fit
ALI−PUB−58041 [1] )c (GeV/Tp0 1 2 3 4 5 6 7
]
-2 )c
) [(
GeV
/y
dT
p/(
dN
2)
dT
pπ
1/(
2e
vN
1/
-510
-410
-310
-210
-110
1
10
pp +
= 5.02 TeVNNsALICE, p-Pb,
< 0.5CMS
y0 <
V0A Multiplicity Classes(Pb-side)
0-5% (64x)
5-10% (32x)
10-20% (16x)
20-40% (8x)
40-60% (4x)
60-80% (2x)
80-100% (1x)
individual fit
ALI−PUB−58045 [1]
Spectra evolution with multiplicity in p–Pb: shown to exhibit behaviour that is qualitatively similar to both pp and
Pb–Pb
Particle ratios
)c (GeV/T
p
0 0.5 1 1.5 2 2.5 3
Ra
tio
0.5
1
1.5
2
2.5
3
3.5
)c (GeV/T
p
0 0.5 1 1.5 2 2.5 3
Ra
tio
0.5
1
1.5
2
2.5
3
3.5
ALICE Preliminary
2+syst2statuncert.=
= 2.76 TeVNN
sPb-Pb,
>=13.4η/dch
N>=1601/=45/
