Novel Quantum Phenomena in the Subatomic Swirls
Chiral Matter Workshop @ NTU Dec. 6~9, 2018
Jinfeng Liao
Indiana University, Physics Dept. & CEEM
Research Supported by NSF & DOE
The Subatomic Swirls
An exciting discovery from STAR Collaboration at RHIC:
The most vortical fluid!
2
Introduction
Nuclear Physics: Exploring the Heart of Matter
nuclear force
matter molecule atoms
atomic nucleus proton
neutron
[a millionth of a mm]
[a trillionth of a mm]
The physical world has a hierarchy of structures.
Most basic entities:
quarks and gluons.
Quantum
Chromodynamics (QCD)
Quantum Chromodynamics (QCD)
The fundamental theory of strong nuclear force:
QCD, a non-Abelian gauge theory of quarks and gluons
Asymptotic Freedom: coupling becomes large at low energy or long distance scale.
⇤QCD ⇠ 200MeV R ⇠ 1 fm
Nobel Prize 2004
QCD Confinement: “The Missing Particles"
This null result is by itself a remarkable FACT of Nature.
Confinement problem:
Biggest challenge withinStandard Model!
Mathematics: one of the seven Millennium Problems!
from Particle Data Group
QCD vacuum as “dual superconductor” with dual Meissner effect?
Color-magnetic topological condensate?
QCD dipole field
Chiral Symmetry: Spontaneous Breaking
Dirac Sea
Lagrangian (SM) mass Constituent
mass
m⇡ ⇡ 140MeV , mn ⇡ 940MeV
Vacuum condensate
It accounts for 99% of the mass of our visible
matter in universe.
QCD as Topological Material
Instantons
Emergent Phenomena in QCD
F. Wilczek
@ QM2014
NP as Quantum Chromo Material Science
This talk will focus on the “hot frontier”.
Temperature
Baryon Density
“Hot
Frontier”
“Force Frontier”
“Dense Frontier”
Quark-Gluon Plasma (QGP):
A Subatomic Quantum Fluid
QCD in Hot Environment
The “super” side is hard, and let’s attack the lambda point from the “right side”, when the system is just about to condense!
Why don’t we do the same for QCD?!
QCD at extreme temperatures:
At high enough T >> Lambda_QCD
A transition to a quark-gluon plasma (QGP) ! [mid ~ late 1970’s]
QGP: A New Phase of Matter
from Lattice QCD
a relativistic pion gas
More precisely,
Hadron Resonance Gas
free QGP
RHIC LHC
* Two benchmarks at low/high T
* A transition regime in the middle
* Crossover (instead of a phase transition)
QGP: A New Phase of Matter
The high T phase of QCD matter (a few hundred MeV & up) is a distinctive new phase, the quark-gluon plasma (QGP).
The liberated quarks & gluons
The restored chiral symmetry
Wuppertal- Budapest
HotQCD
Little Bangs in Heavy Ion Collisions (HIC)
Relativistic Heavy Ion Collider
An artistic presentation:
“nuclei as heavy as bulls,
colliding into new phase of matter”
Large Hadron Collider
The Setup of Heavy Ion Collision
A typical off-central collision.
In-Plane Out-of-Plane
Quark-gluon plasma is created in such collisions!
QGP Shining Brightly!
QGP is hot stuff: about trillion degrees ! Official Guinness World Record:
the highest man-made temperature!
RHIC/LHC
QGP: An Old Phase of Matter
The quark-gluon plasm is an old phase of matter!
The highest ever temperature was in the beginning of universe.
The QGP temperature was available back then.
Anisotropic Explosion: Elliptic Flow
relativistic hydrodynamics
@ 1~ 10 fm scale.
This response is very sensitive to fluid dissipation
from STAR
QGP: Nearly Perfect Quantum Liquid
QGP is a quantum fluid:
s ⇠ n
⌘/s ⇠ pT ⇠ / dB
It has nearly perfect fluidity:
less dissipative than known substance;
very close to conjectured lower bound.
[A recent ravel: cold atomic gas with infinite scattering length]
Vorticity & Magnetic Field
Fascinating New Frontiers
B ~
~
!
QGP fluid in extremely strong vorticity and magnetic fieldsRotating Quark-Gluon Plasma Ly = Abp
s
2 ⇠ 104⇠5~
ˆ z ˆ
x Pz = Aps
2
Pz = +Ap s 2
ˆ z ˆ
x
QGP’s way of accommodating this angular momentum
Quantifying Fluid Rotation
NR UR
Heavy ion collisions:
@ ⇠ fm 1
! ⇠ 1022 s 1
v ⇠ 0.1 c
The averaged vorticity strongly increases toward low beam energy!
Jiang, Lin, JL, PRC2016; Deng & Huang, PRC2016;
Xia, Li, Wang, et al, PRC; Shi, Li, JL, PLB2018; …
Rotating Quark-Gluon Plasma
The angular momentum together with large (+Ze) nuclear charge
—> strong magnetic field!
Strong Electromagnetic Fields
Strong Electromagnetic Fields
• Strongest B field (and strong E field as well) naturally arises!
[Kharzeev,McLerran,Warringa;Skokov,et al; Bzdak-Skokov;
Deng-Huang; Skokov-McLerran; Tuchin; ...]
• “Out-of-plane” orientation (approximately) [Bloczynski-Huang-Zhang-Liao]
E, B ⇠ Z↵EM
R2A ⇠ 3m2⇡
Quantitative simulations confirm the existence of such extreme fields!
Strong Electromagnetic Fields
[STAR measurements of dielectron directly from such fields, PRL2018]
Huang, Liao, et al PLB2012
Spin & Rotational Polarization
Spin-Fluid Coupling
How does a many-body system cope with a sizable angular momentum?
Orbital motion (vorticity);
Spin alignment (polarization).
Fluid vorticity Macroscopic
Individual spin
Microscopic, quantum
???
Spin & Rotational Polarization
Dirac Lagrangian in rotating frame:
Under slow rotation:
Rotational
polarization effect!
Rotational Polarization
Rotational
polarization effect!
For thermally produced particles:
“equal-partition” of angular momentum
~
!
dN / e
!~T· ~J“Fluid Spintronics”
From Vorticity to Spin Polarization
Viscous fluid flow
—> vorticity
—> spin polarization
Fluid Spintronics in the Subatomic Swirls
STAR Collaboration, Nature 2017
Fluid Spintronics in the Subatomic Swirls
STAR Collaboration, Nature 2017
! ⇡ (9 ± 1) ⇥ 1021s 1
The most vortical fluid!
Low energy
High energy
Jiang, Lin, JL, PRC2016
Rotational Suppression of Fermion Pairing
[Yin Jiang, JL, PRL2016]
[Rotational Inhabitation: Chen, Fukushima, Huang, Mameda, PRD2016]
Let us consider pairing phenomenon in fermion systems.
There are many examples:
superconductivity, superfluidity, chiral condensate, diquark, … We consider scalar pairing state, with J=0.
S = ~s~ 1 + ~s2 J = ~~ L + ~S
Rotation tends to polarize ALL
angular momentum, both L and S, thus suppressing scalar pairing.
L~
L~
~
!
Chiral Magnetic Effect in the Subatomic Chiral Matter
Exciting Progress: See Recent Reviews
Prog. Part. Nucl. Phys. 88, 1 (2016)[arXiv:1511.04050 [hep-ph]].
J. Liao, Pramana 84, no. 5, 901 (2015) [arXiv:1401.2500 [hep-ph]].
X.G. Huang, ROPP2016; Hattori, Huang, 2017.
Chiral Anomaly
* C_A is universal anomaly coefficient
* Anomaly is intrinsically QUANTUM effect Chiral anomaly is a fundamental aspect of QFT with chiral fermions.
V
A V
Broken at QM level:
Classical symmetry:
[e.g. pi0—> 2 gamma]
Chiral Restoration in QGP
* Spontaneously broken chiral symmetry in the vacuum is a fundamental property of QCD.
* A chirally symmetric quark-gluon plasma at high temperature is also a fundamental property of QCD!
Can we see direct experimental evidence for that?
Chiral Restoration via Chiral Anomaly
J5µ = JRµ JLµ
@
µJ
5µ= 2iM ¯
5+C
A~E · ~B
Low T
Strong spon. breaking
High T
Quantum Anomaly
Look for pure quantum anomaly effect in hot QGP with chiral symmetry restoration!
The Chiral Magnetic Effect (CME)
J = ~ Q 2
2⇡ 2 µ 5 B ~
Chirality & Anomaly & Topology
Magnetic Field Electric
Current
Q.M. Transport
Intuitive Picture of CME
Intuitive understanding of CME:
Magnetic polarization —>
correlation between micro.
SPIN & EXTERNAL FORCE
Chiral imbalance —>
correlation between directions of SPIN & MOMENTUM
⊗
Transport current along magnetic field
J =~ Q2
2⇡2 µ5 B~
From Micro. Laws To Macro. Phenomena
Micro. Laws:
Symmetry;
Lagrangian;
Conservation laws;
……
Macro. Phenomena:
Thermodynamics;
Transport;
Fluid Dynamics;
……
Quantum Field Theory
Kinetic
Theory Fluid
Dynamics
Weakly Interacting
Strongly Interacting
WHAT ABOU the “SEMI”-SYMMETRY???
i..e ANOMALY?!
— classical symmetry that is broken in quantum theory
CME = Macroscopic Chiral Anomaly
Anomaly -->
Chirality -->
* This is a non-dissipative current!
* Indeed the chiral magnetic conductivity is P-odd but T-even!
(In contrast the Ohmic conductivity is T-odd and dissipative.) CME is a quantum/anomalous transport current
as macroscopic manifestation of microscopic quantum anomaly.
Fluid Dynamics That Knows Left & Right
[Son, Surowka, 2009;…]
conservation law:
constituent relation:
CME CVE
Microscopic quantum anomaly emerges as macroscopic anomalous hydrodynamic currents!
It would be remarkable to actually “see” this new hydrodynamics at work in real world materials!
Looking for CME in Heavy Ion Collisions
The quark-gluon plasma is a subatomic CHIRAL MATTER.
In-Plane Out-of-Plane
Can we observe CME in heavy ion collisions??
1) (nearly) chiral quarks 2) chirality imbalance 3) strong magnetic field
From Gluon Topology to Quark Chirality
QCD anomaly: gluon topology —> chirality imbalance
From CME Current to Charge Separation
[Kharzeev 2004; Kharzeev, McLerran, Warringa,2008;…]
strong radial blast:
position —> momentum
+ +
- -
Very difficult measurement:
* Zero average, only nonzero variance;
* Correlation measurement with significant backgrounds;
* Signal likely small
Latest Exp. Search Status
[From Z. Ye, STAR Summary Talk @ QM2018]
ALICE @ LHC 2.76TeV: signal level possibly about 8~10%
(upper limit ~30%)
CMS @ LHC 5.02TeV: signal level no more than 7%
The trend with beam energy seems in line with expectation!
STAR @ RHIC 200GeV: “
naive” statistical interpretation: ( 8.5 +/- 1.2 ) %
arXiv:1611.04586
arXiv:1711.02496
Badly needed:
Quantitative predictions for CME signal in heavy ion
collisions!
Anomalous Viscous Fluid Dynamics (AVFD)
AVFD:
Anomalous-Viscous Fluid Dynamics
The AVFD Framework
arXiv:1611.04586 arXiv:1711.02496 We now have a versatile tool to
quantitatively understand and answer many important questions about CME in heavy ion collisions!
The AVFD Framework
[We now also have MUSIC-AVFD!]
The AVFD At Work
[arXiv:1611.04586; arXiv:1711.02496]
Zero B Field Nonzero B Field
The AVFD At Work
[arXiv:1611.04586; arXiv:1711.02496]
Left-handed Right-handed
The Charge Separation from AVFD
AVFD Predictions v.s Experimental Data
Excellent agreement!
Shi, Jiang, JL, et al: arXiv:1611.04586 [CPC];
arXiv:1711.02496 [Annals of Physics]
Chiral Magnetic Wave (CMW)
CMW: gapless collective excitation in chiral fluid
—> charge quadrupole of QGP —> elliptic flow splitting [Burnier, Kharzeev, JL, Yee, PRL2011;
& arXiv: 1208.2537]
[STAR, PRL2015]
charge quadrupole due to CMW transport
[STAR@RHIC]
[Also seen by ALICE@LHC]
There Are Electric Fields Too!
Chiral matter in strong electric field:
Chiral Electric Separation Effect (CESE) [Huang, JL, PRL2013; Jiang, Huang, Liao, PRD2014]
QED plasma QCD plasma
Summary & Outlook
Summary: the Subatomic Swirls
Subatomic swirls as the most vortical fluid with the strongest B field
Quark-Gluon Plasma:
A Subatomic Chiral Fluid
The hottest material
The new, 5th state of
matter
The oldest state of matter:
early cosmos
The most perfect fluid
Spin Polarization
CME