Principal Component Analysis of two-particle azimuthal 
correlations in PbPb and pPb collisions at CMS

) is presented in PbPb collisions at 2.76 TeV and high-multiplicity pPb collisions at 5.02 TeV. The data were recorded using the CMS detector at the LHC. It has recently been shown that factorization breaking of two-particle azimuthal correlations can be attributed to the effect of initial-state fluctuations. Using a PCA approach, Fourier coefficients of observed two-particle azimuthal correlations as a function of both particles

p_T

are characterized into leading and sub-leading mode terms. The leading modes are essentially equivalent to anisotropy harmonics (

v_n

) previously extracted from two-particle correlation methods as a function of

p_T

. The sub-leading modes represent the largest sources of factorization breaking. In the context of hydrodynamic models, they are a direct consequence of initial-state fluctuations, particularly providing new insights on the radial excitations of initial-state eccentricity. The results are presented over a wide range of centrality and event multiplicity. Connection to the measurement of

p_T

-dependent flow factorization breaking is also discussed.

Note:

Preliminary results

Data
angular correlation: two-particle
principal component analysis
transverse momentum
initial state: fluctuation
factorization
multiplicity
correlation: two-particle
model: hydrodynamics
rapidity

References(27)

Figures(4)

[1]

Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

PHENIX

Collaboration

•

K. Adcox
(
- Vanderbilt U.
)

et al.

- Nucl.Phys.A 757 (2005) 184-283
•
e-Print:
- nucl-ex/0410003
•
DOI:
- 10.1016/j.nuclphysa.2005.03.086

[2]

Experimental and theoretical challenges in the search for the quark gluon plasma: The STAR Collaboration's critical assessment of the evidence from RHIC collisions

STAR

Collaboration

•

John Adams
(
- Birmingham U.
)

et al.

- Nucl.Phys.A 757 (2005) 102-183
•
e-Print:
- nucl-ex/0501009
•
DOI:
- 10.1016/j.nuclphysa.2005.03.085

[3]

The PHOBOS perspective on discoveries at RHIC

PHOBOS

Collaboration

•

B.B. Back
(
- Argonne
)

et al.

- Nucl.Phys.A 757 (2005) 28-101
•
e-Print:
- nucl-ex/0410022
•
DOI:
- 10.1016/j.nuclphysa.2005.03.084

[4]

Quark gluon plasma and color glass condensate at RHIC? The Perspective from the BRAHMS experiment

BRAHMS

Collaboration

•

I. Arsene
(
- Bucharest U.
)

et al.

- Nucl.Phys.A 757 (2005) 1-27
•
e-Print:
- nucl-ex/0410020
•
DOI:
- 10.1016/j.nuclphysa.2005.02.130

[5]

Harmonic decomposition of two-particle angular correlations in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV

ALICE

Collaboration

•

K. Aamodt
(
- Bergen U.
)

et al.

- Phys.Lett.B 708 (2012) 249-264
•
e-Print:
- 1109.2501
•
DOI:
- 10.1016/j.physletb.2012.01.060

[6]

Elliptic flow of identified hadrons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

ALICE

Collaboration

•

Betty Bezverkhny Abelev
(
- LLNL, Livermore
)

et al.

- JHEP 06 (2015) 190
•
e-Print:
- 1405.4632
•
DOI:
- 10.1007/JHEP06(2015)190

[7]

Measurement of the azimuthal anisotropy for charged particle production in $\sqrt{s_{NN}}=2.76$ TeV lead-lead collisions with the ATLAS detector

ATLAS

Collaboration

•

Georges Aad
(
- Freiburg U.
)

et al.

- Phys.Rev.C 86 (2012) 014907
•
e-Print:
- 1203.3087
•
DOI:
- 10.1103/PhysRevC.86.014907

[8]

Measurement of the distributions of event-by-event flow harmonics in lead-lead collisions at = 2.76 TeV with the ATLAS detector at the LHC

ATLAS

Collaboration

•

Georges Aad
(
- Freiburg U.
)

et al.

- JHEP 11 (2013) 183
•
e-Print:
- 1305.2942
•
DOI:
- 10.1007/JHEP11(2013)183

[9]

Measurement of event-plane correlations in $\sqrt{s_{NN}}=2.76$ TeV lead-lead collisions with the ATLAS detector

ATLAS

Collaboration

•

Georges Aad
(
- Marseille, CPPM
)

et al.

- Phys.Rev.C 90 (2014) 2, 024905
•
e-Print:
- 1403.0489
•
DOI:
- 10.1103/PhysRevC.90.024905

[10]

Centrality Dependence of Dihadron Correlations and Azimuthal anisotropy Harmonics in PbPb Collisions at $\sqrt{s_{NN}}=2.76$ TeV

CMS

Collaboration

•

Serguei Chatrchyan
(
- Yerevan Phys. Inst.
)

et al.

- Eur.Phys.J.C 72 (2012) 2012
•
e-Print:
- 1201.3158
•
DOI:
- 10.1140/epjc/s10052-012-2012-3

[11]

Measurement of the Elliptic Anisotropy of Charged Particles Produced in PbPb Collisions at $\sqrt{s}_{NN}$ =2.76 TeV

CMS

Collaboration

•

Serguei Chatrchyan
(
- Yerevan Phys. Inst.
)

et al.

- Phys.Rev.C 87 (2013) 1, 014902
•
e-Print:
- 1204.1409
•
DOI:
- 10.1103/PhysRevC.87.014902

[12]

Measurement of Higher-Order Harmonic Azimuthal Anisotropy in PbPb Collisions at $\sqrt{s_{NN}}$ = 2.76 TeV

CMS

Collaboration

•

Serguei Chatrchyan
(
- Yerevan Phys. Inst.
)

et al.

- Phys.Rev.C 89 (2014) 4, 044906
•
e-Print:
- 1310.8651
•
DOI:
- 10.1103/PhysRevC.89.044906

[13]

Studies of Azimuthal Dihadron Correlations in Ultra-Central PbPb Collisions at $\sqrt{s_{NN}} =$ 2.76 TeV

CMS

Collaboration

•

Serguei Chatrchyan
(
- Yerevan Phys. Inst.
)

et al.

- JHEP 02 (2014) 088
•
e-Print:
- 1312.1845
•
DOI:
- 10.1007/JHEP02(2014)088

[14]

Transverse Momentum Analysis of Collective Motion in Relativistic Nuclear Collisions

P. Danielewicz
(
- LBL, Berkeley
)
,
G. Odyniec
(
- LBL, Berkeley
)

- Phys.Lett.B 157 (1985) 146-150,
- Lawrence Berkeley Lab. - LBL-18600 (84,REC.FEB.85) 14p,
- Phys. Lett. B157 (1985) 146-150 and Lawrence Berkeley Lab. - LBL-18600 (84,REC.FEB.85) 14p
•
e-Print:
- 2109.05308
•
DOI:
- 10.1016/0370-2693(85)91535-7