Measurements of open heavy-flavour production in pp and p ......T-differential production cross...

Measurements of open heavy-flavour production in pp and p-Pb collisions with ALICE

Sarah LaPointe INFN Torino

For the ALICE collaboration

The 7th international workshop on charm physics May 18-22, 2015

Why study open heavy flavour?

(GeV)s10 210 310 410

b)µ ( cc

σ

10

210

310

410ALICE (total unc.)ALICE extr. unc.ATLAS Preliminary (total unc.)ATLAS extr. unc.LHCb Preliminary (total unc.)PHENIXSTARHERA-B (pA)E653 (pA)E743 (pA)NA27 (pA)NA16 (pA)E769 (pA)NLO (MNR)

ALI−PUB−15089

JHEP 1207 (2012) 191

(GeV)s

210 310 410

b)

µ/d

y (

bb

σd

1

10

210= 2.76 TeV, |y|

Why study open heavy flavour?

‣ Study cold nuclear matter effects, to better evaluate hot matter effects in Pb-Pb collisions

‣ Modification of parton distributions in nuclei

‣ shadowing / gluon saturation at low Bjorken x

‣ kT-broadening from multiple soft scatterings

‣ Study partonic energy loss from initial- and final-state radiation

‣ Investigate potential final-state effects

S. LaPointe Charm 2015: The 7th International Workshop on Charm Physics 3

JHEP 0904(2009) 65

p-Pb collisions

Results from Pb-Pb collisions C. Bianchin (this session)Experimental overview ➜ A. Dainese (this morning)

A Large Ion Collider Experiment

TOF - PID w/ Time Of Flight

TPC - Tracking and PID w/ dE/dx

Muon spectrometer - Trigger, tracking, and

PID

ITS - Trigger, event topology, tracking, PID

Central barrel |η|

dE/dxσe〉dE/dx〈dE/dx -

-10 -8 -6 -4 -2 0 2 4 6 8 10

E/p

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

1

10eK+p π

15/05/2012

=2.76 TeVspp

EMCal Trigger Events

Heavy-flavour production cross sections

S. LaPointe Charm: The 7th international conference on charm physics 2S. LaPointe Charm 2015: The 7th International Workshop on Charm Physics 6

• pQCD predictions describe the data within uncertainties FONLL: JHEP 1210 (2012) 37, GM-VFNS: EPJ C72 (2012) 2082, kT-factorization: PRD 87 (2013) 094022

• Measurements of HF-decay electrons complementary to the high-pT ATLAS result• Similar situation for pp collisions at √s = 2.76 TeV

GeV/c t

p0 5 10 15 20 25

b/G

eV

/c)

µ

(|y

|<0.5

| t /

dp

σd

-210

-110

1

10

210

310

ALICE-1 = 5 nb

int = 7 TeV, Ls, pp

+D

2.1% BR norm. unc. (not shown)± 3.5% lumi, ±

stat. unc.

syst. unc.

FONLL

GM-VFNS

(GeV/c)t

p0 5 10 15 20 25

FO

NL

LD

ata

00.5

1

1.52

2.53

3.5

(GeV/c) t

p0 5 10 15 20 25

GM

-VF

NS

Data

00.5

11.5

22.5

33.5

ALI−PUB−12507

JHEP 1201 (2012) 128, Ds in PLB 178 (2012) 279

)2

dy)

(m

b/(

GeV

/c)

t/(

dp

σ2

) d

tp

π 1

/(2

-910

-810

-710

-610

-510

-410

-310

-210

-110

e→ALICE c, b

e→ATLAS c, b

e, |y| < 0.5→FONLL c, b

e, |y| < 2 excl. 1.37 < |y| < 1.52→FONLL c, b

= 7 TeVspp,

(GeV/c)t

p

-110×4 1 2 3 4 5 6 7 8 910 20 30

Data

/FO

NLL

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

ALI−PUB−16461

ALICE: PRD 86 (2012) 11200 ATLAS: PLB 707 (2012) 438

PLB 708 (2012) 265

pp collisions at √s = 7 TeVD mesons

HF-decay muonsHF-decay electrons


• pT-differential production cross section of electrons from beauty-hadron decays

• Compatibility with FONLL, GM-VFNS and kT-factorization calculations )

2 )c

dy)

(m

b/(

GeV

/T

p/(

dσ

2)

dT

pπ

1/(

2

-810

-710

-610

-510

-410

-310

-210 = 2.76 TeVsALICE pp,

1.9% normalization uncertainty not shown

(a)

e→ c) →b (

data

FONLL factorizationT k

GM-VFNS

Da

ta/T

he

ory

0.51

1.52

2.53

FONLL(b)

Da

ta/T

he

ory

0.51

1.52

2.53

(c) -factorizationTk

)c (GeV/T

p 0 2 4 6 8 10

Data

/Theory

0.51

1.52

2.53

(d)GM-VFNS

ALI-PUB-82148

PLB 738 (2014) 97-108

Electrons from beauty-hadron decays N

orm

aliz

ed

co

un

ts (

a.u

.)

1

10

210

310

PYTHIA e→ c) →b (

e→c Conversions (V0)Dalitz decays

DataConversions (V0)

= 2.76 TeVsALICE pp,

(a)

m)µ (0 d-600 -400 -200 0 200 400 600

Da

ta/M

C

00.5

11.5

22.5

3 Conversions (V0) (b)

ALI-PUB-82084

-3 -2 -1 0 1 2 3

)-1

(r

ad

e-h

)ϕ

∆/d

N (

de

N1/

1

1.5

2

2.5

3

3.5

4 (a) MB Trigger Samplec < 2.5 GeV/e

Tp1.5 <

c > 0.3 GeV/hT

p

| < 0.9η|

/NDF = 19/182χ

= 2.76 TeVsALICE pp,

(rad)ϕ∆-3 -2 -1 0 1 2 3

1

2

3

4

5

6

7

8 e→Data: c,b

MC fit

e→MC: c ) e→ (c →MC: b

(b) EMCal Trigger Sample

c < 6.0 GeV/eT

p4.5 <

c > 0.3 GeV/hT

p

| < 0.7η|

/NDF = 8.5 / 92χ

ALI-PUB-82098

• relatively long lifetime (cτ~500 μm) ➜ broad impact parameter distribution• decay kinematics ➜ ∆φ between electron-hadron wider than for other sources

Beauty-hadron decays

FONLL: JHEP 1210 (2012) 37, GM-VFNS: EPJ C72 (2012) 2082, kT -factorization: PRD 87 (2013) 094022

Impact-parameter analysis

electron-hadron azimuthal correlation

pp collisions at √s = 7 TeV

(rad)ϕ∆-1 0 1 2 3 4 5

)-1 -

base

line

(rad

ϕ∆da

ssoc

Nd DN1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

scale uncertainty-10%+13%

=7 TeV Data spp =7 TeVsSimulations, pp

Pythia8Pythia6, Perugia2010Pythia6, Perugia2011

baseline uncertainty

D meson - charged particle correlation

ALICE Preliminary| < 1.0 η∆, |c > 1.0 GeV/assoc

Tp, c < 16 GeV/D

Tp8 <

*+,D+,D0Average D

ALI−PREL−78716 (rad)ϕ∆

-1 0 1 2 3 4 5

)-1 -

base

line

(rad

ϕ∆da

ssoc

Nd DN1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5


=7 TeV Data spp =7 TeVsSimulations, pp

Pythia8Pythia6, Perugia2010Pythia6, Perugia2011



ALICE Preliminary| < 1.0 η∆, |c > 0.5 GeV/assoc

Tp, c < 8 GeV/D

Tp5 <

*+,D+,D0Average D

ALI−PREL−78598


• Baseline subtracted azimuthal correlation of D mesons and charged hadrons• Different PYTHIA tunes consistent with the measurement• Data from Run-II at the LHC will provide more precision ➜ constrain models

D meson-hadron azimuthal correlationsMeasure the associated hadron yield on the near (∆φ around 0) and away side (∆φ around π)

• Sensitive to quark fragmentation• Insight into cc production mechanisms5 < pTD < 8 GeV/cpTAssoc. > 0.5 GeV/c

8 < pTD < 16 GeV/cpTAssoc. > 1 GeV/c

PYTHIA8Perugia 2010Perugia 2011

pp collisions at √s = 7 TeV

〉T

pdy

/dN

2 d〈)

/ T

pdy

/dN

2(d

5

10

15

20

25

c


Multiplicity dependence of D-meson production

Self-normalized D-meson yields as a function of charged-particle multiplicity

〉T

pdy

/dN

2 d〈)

/ T

pdy

/dN

2(d

5

10

15

20

25

c




〉T

pdy

/dN

2 d〈)

/ T

pdy

/dN

2(d

5

10

15

20

25

c < 2 GeV/T

p 1 < c < 4 GeV/

Tp 2 <

c < 8 GeV/T

p 4 < c < 12 GeV/

Tp 8 <

c < 20 GeV/T

p 12 <

= 7 TeVsALICE, pp |


• Measured for different D-meson species

• Increase of D-meson per-event yield with increasing charged-particle yield

• Within the uncertainties, no pT-dependence of D-meson yield vs. multiplicity observed

• Similar rising trend observed for J/ψ mesons central and forward rapidity PLB 712(2012)165

• Increase of beauty production with increasing multiplicity



〉T

pdy

/dN

2 d〈)

/ T

pdy

/dN

2(d

5

10

15

20

25

c < 2 GeV/T

p 1 < c < 4 GeV/

Tp 2 <

c < 8 GeV/T

p 4 < c < 12 GeV/

Tp 8 <

c < 20 GeV/T

p 12 <

= 7 TeVsALICE, pp |


• Assessment of initial-state, cold nuclear matter effects

• Investigate possible final-state effects  

p-Pb collisions at √s = 5.02 TeV


Nuclear modification factor for HF-decay electrons

• RpPb of HF-decay electrons compatible with unity• Data described by FONLL+EPS09 parametrization of shadowing, within the

uncertainties NPB 373(1992)295, JHEP 0904 (2009) 065• RpPb of electrons from beauty hadron decays is also compatible with unity

(GeV/c)T

p0 2 4 6 8 10 12 14

nucl

ear

modifi

atio

n fact

or

0.5

1

1.5

2

2.5

3

normalization uncertainty

)/2, TPC-TOF, ALICE reference-

+ e+

(e→ALICE b,c

)/2, TPC-EMCal, ALICE reference-

+ e+

(e→ALICE b,c

)/2, TPC-EMCal, FONLL reference-

+ e+

(e→ALICE b,c

FONLL + EPS09 shad.

< 1.06CMS

= 5.02 TeV, min. bias, -0.14 < yNNsp-Pb,

ALI−DER−53763

RpPb =d�pPb/dpT

A ⇥ d�pp/dpT


Nuclear modification factor for HF-decay electrons

• RpPb of HF-decay electrons compatible with unity• Data described by FONLL+EPS09 parametrization of shadowing, within the

uncertainties NPB 373(1992)295, JHEP 0904 (2009) 065• RpPb of electrons from beauty-hadron decays is also compatible with unity

)c (GeV/T

p0 2 4 6 8 10 12 14

pP

bR

0.5

1

1.5

2

2.5

3 e→ALICE b,c

e→ c) →ALICE b (

normalization uncertainty

ALICE Preliminary

< 0.14CMS

y = 5.02 TeV, min. bias, -1.06 < NNsp-Pb,

ALI−PREL−76745

RpPb =d�pPb/dpT

A ⇥ d�pp/dpT


Nuclear modification factor for HF-decay muons

• RpPb of HF-decay muons at forward rapidity compatible with unity• RpPb of HF-decay muons at backward slightly greater than unity at low pT• Data described by models that include cold nuclear matter effects

MNR pQCD calculation with EPS09 parametrization of shadowing NPB 373(1992)295, JHEP 0904 (2009) 065I. Vitev - coherent scattering, kT-broadening, and energy loss in cold nuclear matter PRC 75 (2007) 064906 Z. B. Zhang et. al. - incoherent multiple scattering PLB 740 (2015) 23

)c (GeV/T

p0 2 4 6 8 10 12 14 16

pP

bR

0

0.5

1

1.5

2

2.5 c,b decays←±µ = 5.02 TeV, NNsp-Pb


Nuclear modification factor for D mesons

• RpPb of D mesons compatible with unity within the pT range covered• The RpPb can be described by:

MNR pQCD calculation with EPS09 parametrization of shadowing NPB 373(1992)295, JHEP 0904 (2009) 065I. Vitev - coherent scattering, kT-broadening, and energy loss in cold nuclear matter PRC 75 (2007) 064906 CGC - color glass condensate NPA 920 (2013) 78.

)c (GeV/T

p0 5 10 15 20 25

pP

bR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6 *+, D

+, D

0Average D



• D-meson production vs. multiplicity ➜ similar trend in pp and p-Pb collisions • pp collisions: high multiplicity events attributed to MPI• p-Pb collisions: high multiplicity events also from multiple binary nucleon-

nucleon collisions • CMS reports similar trend from Υ measurements in pp and p-Pb collisions

〉T

pdy

/dN

2 d〈)

/ T

pdy

/dN

2(d

5

10

15

20

25

= 7 TeVspp, c

(rad)ϕ∆-1 0 1 2 3 4 5 6

)-1) (

rad

ϕ∆

/ d

eh) (

dNe

(1 /

N

0.0

0.5

1.0

1.5

2.0 = 5.02 TeVNNsp-Pb,

< 2.0 GeV/ceT

1.0 < p

< 2.0 GeV/chT

0.5 < p

(e from c,b)-h correlation

| < 1.6η∆| < 0.9, |η|

-1Global normalization uncertainty = 0.06 rad

p-Pb, V0A Multiplicity class: 0 - 20 %p-Pb, V0A Multiplicity class: 20 - 60 %p-Pb, V0A Multiplicity class: 60 - 100 %Syst. on ped. estimationSyst. from secondary particles

= 7 TeVspp, pp, stat. uncertainty

ALI−PREL−61949


HF electron-hadron correlations in p-Pb collsions

(rad)ϕ∆ -1 0 1 2 3 4

)-1 (r

adη

∆) p

er

ϕ∆

/ d

h) (

dNe

(1 /

N

3.0

3.1

3.2

3.3

3.4

= 5.02 TeVNNsp-Pb,

(0-20%) - (60-100%), Multiplicity Classes from V0A

< 2.0 GeV/ceT

1.0 < p

< 2.0 GeV/chT

0.5 < p

| < 1.6η∆| < 0.9, |η|



ALI−PREL−62034

(0-20%)-(60-100%)

(rad)ϕ∆-1 0 1 2 3 4 5 6

)-1) (

rad

ϕ∆

/ d

eh) (

dNe

(1 /

N

0.0

0.5

1.0

1.5

2.0

2.5

3.0 = 5.02 TeVNNsp-Pb,

< 4.0 GeV/ceT

2.0 < p < 2.0 GeV/ch

T0.5 < p


| < 1.6η∆| < 0.9, |η|


p-Pb, V0A Multiplicity class: 0 - 20 %p-Pb, V0A Multiplicity class: 20 - 60 %p-Pb, V0A Multiplicity class: 60 - 100 %Syst. on ped. estimationSyst. from secondary particles

= 7 TeVspp, pp, stat. uncertainty

ALI−PREL−61956

1 < ptriggerT < 2 GeV/c 2 < ptriggerT < 4 GeV/c

In high multiplicity events:At low electron pT a hint of near- and away-side enhancement

Remove jet contribution by subtracting low multiplicity events

Indication for double-ridge structure, as observed for light-flavor two particle correlations. PLB 719 (2013) 29, PLB 726 (2013) 164

HF possibly affected by the processes consistent with long-range correlations in ∆η of light-flavour hadrons

Initial state: CGC arXiv:1302.7018Final state: Hydrodynamics PLB 718 (2013) 1557

(rad)

ϕ∆ -1

01

23

4

η∆ -1.5

-1.0-0.5

0.00.5

1.01.5

)-1

) (ra

dϕ

∆dη∆

/ d

hN2) (

de

(1 /

N

3.0

3.1

3.2

= 5.02 TeVNNsp-Pb, (0-20%) - (60-100%), Multiplicity Classes from V0A(e from c,b)-h correlation

< 2.0 GeV/ceT

1.0 < p < 2.0 GeV/ch

T0.5 < p

ALI−PREL−62026

(0-20%)-(60-100%)

— pp √s = 7 TeVp-Pb multiplicity classes0-20%20-60%60-100%

For all: 0.5

(rad)ϕ∆-1 0 1 2 3 4 5

)-1

- b

ase

line (

rad

ϕ∆

d

ass

oc

Nd

DN1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

scale uncertainty p-Pb-9%+12%

scale uncertainty pp-10%+13%

=7 TeVspp

=5.02 TeVNN

sp-Pb baseline uncertainty pp

baseline uncertainty p-Pb


ALICE Preliminary

| < 1.0 η∆, |c > 0.5 GeV/assocT

p, c < 8 GeV/DT

p5 <

*+,D+,D0Average D

ALI−PREL−79970

(rad)ϕ∆-1 0 1 2 3 4 5

)-1

- b

ase

line (

rad

ϕ∆

d

ass

oc

Nd

DN1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4


=5.02 TeV Data NN

sp-Pb

=5.02 TeVsSimulations, pp Pythia8Pythia6, Perugia2010Pythia6, Perugia2011



ALICE Preliminary

| < 1.0 η∆, |c > 0.5 GeV/assocT

p, c < 16 GeV/DT

p8 <

*+,D+,D0Average D

ALI−PREL−79835


D meson-hadron correlations in p-Pb collisions

Azimuthal correlation of D mesons with charged hadrons in pp and p-Pb collisions

5 < pTD < 8 GeV/c, pTAssoc. > 0.5 GeV/c 8 < pTD < 16 GeV/c, pTAssoc. > 0.5 GeV/c

• Distributions from pp and p-Pb collisions are comparable• Within the uncertainties the p-Pb measurement is consistent with various PYTHIA tunes • Better constraints of PYTHIA tunes with improved statistics available in Run-II at the LHC


Summary and outlookpp collisions• Measured production cross sections allow us to test various pQCD predictions

• FONLL, GM-VFNS, kT-factorization predictions are in agreement with data• Heavy quark fragmentation studies via D-meson azimuthal correlations

• Consistent with various PYTHIA tunes• Heavy-flavour hadron yield vs. multiplicity

• With increasing multiplicity, yield increases more than linearly • Models including MPI contributions reproduce the observed trend

p-Pb collisions• Heavy-flavour hadron yields

• No strong suppression observed with respect to pp collisions• Increasing yields with increasing event multiplicity, as observed in pp collisions

• D-meson azimuthal correlations• Consistent with various PYTHIA tunes

• Electron-hadron azimuthal correlations at low pT• Double-ridge structure observed. CGC, hydrodynamic expansion, some other mechanism?

Outlook• Statistically larger data sample from Run-II at the LHC• More precise measurements of azimuthal correlations, beauty, and heavy flavour in jets

Extras

QpPb dependence of event activity

) c (GeV/T

p 0 5 10 15 20 25 30

pro

mpt D

mu

lt

pP

bQ

0

0.5

1

1.5

2

2.5

3

0-20%

20-40%

40-60%

60-100%

ALICE Preliminary = 5.02 TeV

NNsp-Pb,

Filled markers : pp rescaled reference-extrapolated reference

TpOpen markers: pp

Measurements of open heavy-flavour production in pp and p ......T-differential production cross...

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Transcript of Measurements of open heavy-flavour production in pp and p ......T-differential production cross...