Subatomic Smoke Rings:�Polarization and toroidal vorticity in the QGP

Mike Lisa, Ohio State University

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LBNL Heavy Hadron Ion Tea

Outline

• Brief motivation and review of hyperon polarization in heavy ion collisions
• Ann.Rev.Nucl.Part.Sci. 70 (2020) 395-423; arxiv:2003.03640

​

• Interesting structures at forward rapidity in A+A – model calculations
• Ivanov, Soldatov, Toneev, Fu, Xu, Huang, Song, Baznat, Gudima, Sorin, Teryaev, Usubov, Deng, Wei, Xia, Li, Tang, Wang, Zinchenko…

​

• Interesting, uncharted directions – hydro calculations
• p+A collisions - PRC104 (2021) 011901; arXiv:2101.10872
• jets in expanding QGP fluid – PLB820 (2021) 136500; arXiv:2102.11919

​

• Summary

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3C Collaboration:

J. Barbon, D. Chinellato, W. Serenone, C. Shen, J. Takahashi, G. Torrieri, MAL

Standard model of H.I.C. : viscous hydrodynamics

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& many more terms...

Phase structure, EoS, transport coefficients

movies by Bjorn Schenke

Standard model of H.I.C. : viscous hydrodynamics + Cooper-Frye

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fluid cell

• Dynamic evolution of locally equilibrated matter
• Hadronization/freezeout driven by conservation laws (and…?)
• emitted particles (measurable!) reflect properties of parent fluid cells

movies by Bjorn Schenke

hadrons

fluid

Standard model of H.I.C. : viscous hydrodynamics + Cooper-Frye

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fluid cell

• chemical potentials
• temperature

• Dynamic evolution of locally equilibrated matter
• Hadronization/freezeout driven by conservation laws (and…?)
• emitted particles (measurable!) reflect properties of parent fluid cells
• Yields

movies by Bjorn Schenke

hadrons

• flavors
• yield

fluid

Update: Andronic et al Nature 561 (2018) 7723, 321; arxiv 1710.09425

Standard model of H.I.C. : viscous hydrodynamics + Cooper-Frye

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fluid cell

• chemical potentials
• temperature
• collective velocity

• Dynamic evolution of locally equilibrated matter
• Hadronization/freezeout driven by conservation laws (and…?)
• emitted particles (measurable!) reflect properties of parent fluid cells
• Yields
• longitudinal, transverse distributions

movies by Bjorn Schenke

hadrons

• flavors
• yield
• momentum

fluid

Standard model of H.I.C. : viscous hydrodynamics + Cooper-Frye

LBNL Hadron Ion Tea - by zoom - May 2022

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fluid cell

• chemical potentials
• temperature
• collective velocity

• Dynamic evolution of locally equilibrated matter
• Hadronization/freezeout driven by conservation laws (and…?)
• emitted particles (measurable!) reflect properties of parent fluid cells
• Yields
• longitudinal, transverse distributions
• azimuthal flow anisotropy

movies by Bjorn Schenke

hadrons

• flavors
• yield
• momentum

fluid

finer

detail

Rotational substructure of noncentral collisions

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fluid cell

• chemical potentials
• temperature
• collective velocity
• vorticity

• Dynamic evolution of locally equilibrated matter
• Hadronization/freezeout driven by conservation laws (and…?)
• emitted particles (measurable!) reflect properties of parent fluid cells
• Yields
• longitudinal, transverse distributions
• azimuthal flow anisotropy
• polarization

hadrons

• flavors
• yield
• momentum
• polarization

fluid

finer

detail

Becattini, Karpenko, MAL, Upsal, Voloshin, PRC 2017

Rotational substructure of noncentral collisions

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fluid cell

• chemical potentials
• temperature
• collective velocity
• vorticity

• Dynamic evolution of locally equilibrated matter
• Hadronization/freezeout driven by conservation laws (and…?)
• emitted particles (measurable!) reflect properties of parent fluid cells
• Yields
• longitudinal, transverse distributions
• azimuthal flow anisotropy
• polarization

hadrons

• flavors
• yield
• momentum
• polarization

fluid

finer

detail

Becattini, Karpenko, MAL, Upsal, Voloshin, PRC 2017

First observation of fluid vorticity-polarization coupling

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“Spin hydrodynamic generation” Takahashi, et al. Nat. Phys. 12 (2016) 52

Friction with walls induces vorticity

Vorticity of bulk 🡪 polarization of constituents (& spin voltage etc)

• direction of vorticity known
• atomic alignment measured

Takahashi knew direction of angular momentum

“This opens a door to the new field of fluid spintronics”

First observation of fluid vorticity-polarization coupling

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“Spin hydrodynamic generation” Takahashi, et al. Nat. Phys. 12 (2016) 52

• direction of vorticity known
• atomic alignment measured

Takahashi knew direction of angular momentum

“This opens a door to the new field of fluid spintronics”

Second observation:

Nature 548 (2017) 62

Global Lambda Polarization

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• Measured global polarization in good agreement with standard hydro predictions [1]
• Three-fluid hydro, especially important at low root(s) [2]
• Transport calculations (coarse-graining to calculate vorticity) [3,4] & kinetic+coalescence [5]

[1] Karpenko I, Becattini F. Eur. Phys. J. C77:213 (2017)

[2] Ivanov YB, Toneev VD, Soldatov AA. Phys. Rev. C100:014908 (2019)

[3] Li H, Pang LG, Wang Q, Xia XL. Phys. Rev. C96:054908 (2017)

[4] Vitiuk O, Bravina LV, Zabrodin EE arXiv:1910.06292 [hep-ph] (2019)

[5] Sun Y, Ko CM. Phys. Rev. C96:024906 (2017)

Lambda polarization is a well-understood/calibrated tool to access fluid substructure at the finest possible scale.

Ann. Rev. Nucl. Part. Sci. 70 (2020) 395

Consistency: other hyperons

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AMPT calculation

• mass & spin dependence

Wei, Deng, & Huang

PRC99 014905 (2019)

Consistent with common fluid vorticity

Hyperon polarization is a well-understood/calibrated tool to access fluid substructure at the finest possible scale.

STAR, Phys. Rev. Lett. 126, 162301 (2021); arxiv:2012.13601

In another direction – longitudinal polarization

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(By symmetry, must be quadrupole)

naïve cartoon

+

+

-

-

In another direction – longitudinal polarization

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(By symmetry, must be quadrupole)

naïve cartoon

+

+

-

-

Tension… and insight?

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AMPT+hydro Wu, Pang, Huang, Wang PR Res 1(2019)033058

“Which kind of vorticity” to use?

theoretically favored^[1]

“works”

[1] Becattini PRL108:244502 (2012)

Tension… and insight?

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AMPT+hydro Wu, Pang, Huang, Wang PR Res 1(2019)033058

“Which kind of vorticity” to use?

theoretically favored^[1]

“works”

[1] Becattini PRL108:244502 (2012)

Alzhrani, Ryu, Shen arxiv:2203.15718

New “shear-induced polarization” terms

BPP

LY

Becattini, Buzzegoli, Palermo PLB 820, 136519 (2021); arXiv:2103.10917

Liu and Yi Yin, JHEP 07, 188 (2021), arXiv:2103.09200

Circular polarization in central A+A

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Xia, Li, Tang, Wang PRC 98, 024905 (2018)

Circular polarization in central A+A

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quantifying smoke-ring structure

PRC104 (2021) 011901

Xia, Li, Tang, Wang PRC 98, 024905 (2018)

these are vorticity vectors, not flow velocities

Rings at below-RHIC energy

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Baznat, Gudima, Sorin, Teryaev PRC93, 031902(R) (2016)

• Helicity separation in heavy-ion collisions (QGSM)�Baznat, Gudima, Sorin, Teryaev PRC88, 061901(R) (2013)
• Vorticity and hydrodynamic helicity in heavy-ion collisions in the HSD model�Teraev & Usubov PRC92 014906 (2015)
• Femto-vortex sheets and hyperon polarization in heavy-ion collisions (QGSM)�Baznat, Gudima, Sorin, Teryaev PRC93, 031902(R) (2016)
• Vorticity in heavy-ion collisions at the JINR NICA (3FD)�Ivanov & Soldatov, PRC 95, 054915 (2017)
• Vortex rings in fragmentation regions in heavy-ion collisions at √sNN = 39 GeV (3FD) �Ivanov & Soldatov PRC97, 044915 (2018)
• Vorticity structure and polarization of Λ hyperons in heavy-ion collisions (PHSD)�Zinchenko, Sorin, Teryaev, Baznat DSPIN-2019 (2020)

​

• Significant attention to structure in space
• Focus of observable implications seems to center on
• identifying forward rapidity as important
• convolution with directed flow affecting global polarization

Teraev & Usubov PRC92 014906 (2015)

Same observations at higher energy

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Ivanov & Soldatov PRC97, 044915 (2018)

Transverse flow should render the vortex rings themselves visible!

root(s) = 39 GeV

• don’t just worry about “accidental” effect on global polarization!

Same observations at higher energy

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Ivanov & Soldatov PRC97, 044915 (2018)

Transverse flow should render the vortex rings themselves visible!

root(s) = 39 GeV

root(s) = 200, 2700 GeV

Xia, Li, Tang, Wang Phys. Rev. C 98, 024905 (2018)

• don’t just worry about “accidental” effect on global polarization!

Development of toroidal vorticity in MUSIC

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Au+Au at 200 GeV

Bjorken flow profile

MUSIC hydrodynamics, with baryon currents

Schenke, Jeon, Gale PRC82 (2010) 014903

Schenke, Shen, Tribedy PRC102 (2020) 044905

PRC104 (2011) 011901

color axis:

Rings predicted at all energies– can they be observed?

• This is a unique predicted structure! Observation would represent a compelling demonstration of fluid structure at the extremes of rapidity & energy

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• Observable at HADES, STAR FXT�(NICA??)

Focused forward

• in principle possible at STAR with forward tracking upgrade

Focused forward

• difficult at STAR@RHIC or ATLAS/CMS/ALICE@LHC without forward tracking upgrade

Teraev & Usubov PRC92 014906 (2015)

Baznat, er al, PRC93, 031902(R) (2016)

Xia, Li, Tang, Wang PRC98, 024905 (2018)

Ivanov & Soldatov PRC97, 044915 (2018)

Seeing the rings

• This is a unique predicted structure! Observation would represent a compelling demonstration of fluid structure at the extremes of rapidity & energy

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Pb+Pb event

Note: No Event Plane Necessary!

Focused forward

• Difficult at STAR@RHIC or ATLAS/CMS/ALICE@LHC without forward tracking upgrade
• LHCb ideal to observe this structure

Michael Winn, ERICE, 2016

Polarization about a local disturbance

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Helmholtz (1867): Persistent vortical toroids (smoke rings) are quintessential fluid behavior

​

Vortex rings about the jet direction:

• Betz/Gyulassy/Torrieri, PRC76 (2007) 044901
• Tachibana/Hirano, NPA904-905 (2013) 1023c
• W. Matioli et al, PLB820 (2021) 136500

Jet-induced toroidal vorticity in MUSIC

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Jet-induced toroidal vorticity

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W. Matioli et al, PLB820 (2021) 136500

Experimentally challenging, but potentially rich!

• early-stage fluid behaviour?
• nature of energy loss in fluid
• sensitivity to transport coefficients

Toroidal vorticity

t = jet direction

MUSIC hydro with embedded jet

What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”

​

​

​

• multi-particle correlation 🡪�though… not uniquely hydro prediction, �e.g.: Dusling et al, PRD 97, 016014 (2018)

​

​

​

​

​

​

• with well-chosen initial conditions and �pre-equilibrium effects, hydro evolution�seems to reproduce 2-particle anisotropy!

​

​

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Nagle & Zajc, Ann.Rev.Nucl.Part.Sci. 68 (2018)

What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”
• if everything is hydro, are we confident that anything is hydro?
• much of the supporting evidence comes from v_n… can we find a novel, hydro-characteristic test?

​

• “Every time you break a symmetry, you learn something”^* (v2, v1, polarization!)
• broken forward/backward symmetry 🡪 potentially interesting initial state

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p

Au

^* Urs Wiedemann

What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”
• if everything is hydro, are we confident that anything is hydro?
• much of the supporting evidence comes from v_n… can we find a novel, hydro-characteristic test?

​

• “Every time you break a symmetry, you learn something”^* (v2, v1, polarization!)
• broken forward/backward symmetry 🡪 potentially interesting initial state

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proton

^* Urs Wiedemann

What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”
• if everything is hydro, are we confident that anything is hydro?
• much of the supporting evidence comes from v_n… can we find a novel, hydro-characteristic test?

​

• “Every time you break a symmetry, you learn something”^* (v2, v1, polarization!)
• broken forward/backward symmetry 🡪 potentially interesting initial state

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(b) Radial-gradient flow profile

See also S. Voloshin, Hirschegg 2017

^* Urs Wiedemann

What about p+A collisions…?

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(a)

(b)

See also S. Voloshin, Hirschegg 2017

(b) Radial-gradient flow profile

• Basic observables are ~identical in these scenarios

What about p+A collisions…?

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• Basic observables are ~identical in these scenarios
• Vorticity is very different

(a)

(b)

See also S. Voloshin, Hirschegg 2017

(b) Radial-gradient flow profile

Relation to Takahashi geometry

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(b) Radial-gradient flow profile

The experimental geometry was not this

It was flow thru capillary tube:

Jet-induced vorticity/polarization

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Willian Serenone’s talk

small stuff blasting through stuff

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p+Au at 200 GeV

(a)

(b)

MUSIC hydrodynamics, with baryon currents

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color axis:

Snaphots

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smooth-on-smooth, b=0�collisions at RHIC

PRC104 (2021) 011901; arxiv: 2101.10872

Fluid ➞ particles (vorticity ➞ polarization)

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Observing the ”smoke tubes”

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• similar effect for all vorticity “flavors”
• hyperon and anti-hyperon are similar

Observing the ”smoke tubes”

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• similar effect for all vorticity “flavors”
• hyperon and anti-hyperon are similar

PRC104 (2021) 011901; arxiv: 2101.10872

Nontrivial dynamics for long lifetime

fluctuating initial conditions

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[1] Shen, Alzhrani, PRC102 (2020) 014909 (2020)

• Event-by-event calculation with lumpy initial conditions, following prescription in [1]�🡪 little difference with smooth initial conditions

​

• reduced R_spin for more symmetric system

Interpolating between the scenarios

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f=100%

f=0%

f=15%

• For Au+Au at 200 GeV (11 GeV), global polarization calls for f=15% (50%)
• Ryu, Jupic, Shen: 2106.08125
• unclear whether this translates to p+A

​

• Even with low f, substantial signal

Reality may lie between the extremes…

Chinellato, MAL, Serenone, Shen, Takahashi, Torrieri in preparation

Effect of shear terms

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[1] F. Becattini, M. Buzzegoli, and A. Palermo �Phys. Lett. B 820, 136519 (2021); arXiv:2103.10917

[2] Shuai Y. F. Liu and Yi Yin�JHEP 07, 188 (2021), arXiv:2103.09200

[1]

[2]

(c.f talks by Buzzegoli and Fu in session T02 Tuesday)

• nontrivial / non-intuitive effect on R
• Large difference in effects predicted by the two prescriptions
• Effect at midrapidity remains

Experimental issues

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Challenge: large topological dependence of efficiency

• artifacts complicated and ~10% (or more)
• will affect any tracking detector
• must flip B-field to cancel artifact

STAR PRC104 (2021) L061901

c/o Joey Adams

Experimental issues

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Challenge: large topological dependence of efficiency

• artifacts complicated and ~10% (or more)
• will affect any tracking detector
• must flip B-field to cancel artifact

Advantage:

• no event plane needed!�🡪 measuring ~1% toroidal polarization is much easier than 1% global polarization (for same stats)

Summary

• A+A / p+A collisions generate complex flow structures; probed by vorticity at small scale
• Circular vorticity pattern predicted for b=0 collisions at all energies
• LHCb – take a look!
• A hydro system with p+A initial conditions could naturally generate a vortical toroid configuration
• similar to jet “blasting through”
• Helmholtz (1867): Persistent vortical toroids (smoke rings) are quintessential fluid behavior
• would be a compelling evidence for hydro nature of the smallest system
• Experimentally observable (R)
• distinct from hadronic processes by particle/antiparticle similarity, eta dependence
• challenging to observe few % effect, but not daunting - flip B-field
• We should explore this unique structure @ RHIC, LHC (while we can…)

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João Prado Barbon, David Chinellato, Willian Serenone, Jun Takahashi, Giorgio Torrieri

University of Campinas (Unicamp)

Chun Shen

Wayne State University

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Habich, Nagle, Romatschke, Eur. Phys. J. C (2015) 75:15

A new idea

arXiv:2101.10872

​

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What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”

​

​

​

• multi-particle correlation 🡪�though… not uniquely hydro prediction, �e.g.: Dusling et al, PRD 97, 016014 (2018)

​

​

​

​

​

​

• with well-chosen initial conditions and �pre-equilibrium effects, hydro evolution�seems to reproduce 2-particle anisotropy!

​

​

LBNL Hadron Ion Tea - by zoom - May 2022

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Nagle & Zajc, Ann.Rev.Nucl.Part.Sci. 68 (2018)

What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”
• if everything is hydro, are we confident that anything is hydro?
• much of the supporting evidence comes from v_n… can we find a novel, hydro-characteristic test?

​

• “Every time you break a symmetry, you learn something”^* (v2, v1, polarization!)
• broken forward/backward symmetry 🡪 potentially interesting initial state

LBNL Hadron Ion Tea - by zoom - May 2022

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p

Au

^* Urs Wiedemann

What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”
• if everything is hydro, are we confident that anything is hydro?
• much of the supporting evidence comes from v_n… can we find a novel, hydro-characteristic test?

​

• “Every time you break a symmetry, you learn something”^* (v2, v1, polarization!)
• broken forward/backward symmetry 🡪 potentially interesting initial state

LBNL Hadron Ion Tea - by zoom - May 2022

57

proton

^* Urs Wiedemann

What about p+A collisions…?

• Do such collisions really form “the smallest droplet of QGP?”
• if everything is hydro, are we confident that anything is hydro?
• much of the supporting evidence comes from v_n… can we find a novel, hydro-characteristic test?

​

• “Every time you break a symmetry, you learn something”^* (v2, v1, polarization!)
• broken forward/backward symmetry 🡪 potentially interesting initial state

LBNL Hadron Ion Tea - by zoom - May 2022

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(b) Radial-gradient flow profile

See also S. Voloshin, Hirschegg 2017

^* Urs Wiedemann

What about p+A collisions…?

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(b) Radial-gradient flow profile

Peek ahead: MUSIC

hydro calculations give

same dN/dη

(a)

(b)

See also S. Voloshin, Hirschegg 2017

What about p+A collisions…?

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As in A+A collisions,

shear & continuity 🡪 vorticity

(b) Radial-gradient flow profile

See also S. Voloshin, Hirschegg 2017

Ubiquitous feature of fluid systems – toroidal vortex

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Small “thrust” initial conditions 🡪 persistent expanding toroidal vortex

​

see also H. Helmholtz, Phil. Jour. Science 33 485 (1867)

Ubiquitous feature of fluid systems – toroidal vortex

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Takahashi, et al, Nature Phys. 12 (2016) 52-56

Quantifying the ring structure

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Non-relativistic:

[1] MAL, Barbon, Chinellato, Serenone, Shen, Takahashi, Torrieri

arxiv:2101.10872

Quantifying the ring structure

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Non-relativistic:

[1] MAL, Barbon, Chinellato, Serenone, Shen, Takahashi, Torrieri

arxiv:2101.10872

Relativistic:

(thermal vorticity)

“Relevant” vorticity depends on mass of particle of interest, temperature, and hypersurface ^[1]

Hydro response - movie

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Au+Au at 200 GeV

Bjorken flow profile

MUSIC hydrodynamics, with baryon currents

Schenke, Jeon, Gale PRC82 (2010) 014903

Schenke, Shen, Tribedy PRC102 (2020) 044905

Hydro response - movies

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p+Au at 200 GeV

(a)

(b)

MUSIC hydrodynamics, with baryon currents

Hydro response - movies

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p+Pb at 5.02 TeV

(a)

(b)

MUSIC hydrodynamics, with baryon currents

Snaphots

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smooth-on-smooth, b=0�collisions at RHIC

arxiv:2101.10872

Experimental observable

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Observable

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• not trivial
• antiLambda similar but not identical to Lambda
• (baryon currents in MUSIC)
• negative shift at LHC
• ~2%, on same order as polarizations measured at RHIC
• and no EP needed!

​

• Distinct from hadronic “production plane” polarization:
• symmetry in rapidity
• antiLambda signal

6

4

2

0

-2

Non-trivial dynamics takes over at large times

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Also seen with X+Au

where X is smaller than Au but larger than proton

Reminder from 1970’s (through 2010’s)

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production-plane polarization in p+A collisions.

• Same observable as ours!
• high-x signal
• ~independent of target (p, Be, C, Cu, W)
• ~independent of energy (only measured to ~40 GeV)
• odd in rapidity for p+p, but also p+A
• no signal for anti-Lambdas

HERA-B PLB638 (2006) 415

NA48 p+N(?) sqrt(sNN) = 29 GeV

E799 p+Be sqrt(sNN) = 39 GeV

HERA-B p+W,C sqrt(sNN) = 41.6 GeV

x

+

parameterization

Another geometry – “jet” through expanding plasma

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image by Kalyan Dey

Willian Serenone, et al, arXiv:2102.11919

Example case

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ATLAS, Phys. Rev. Lett. 105, 252303

Willian Serenone, et al, arXiv:2102.11919

Smooth initial conditions by averaging 3D Trento ICs with b=0

• energy density adjusted to reproduce measured multiplicity (in MUSIC)

“lost”: E=57.5 GeV, p=42.5 GeV/c

• assume completely thermalized

​

Landau matching with fluid 🡪 bullet with

• 𝛆 = 30 GeV/V at v_x = 0.7
• R_bullet = 0.5 fm.
• initial position at center of plasma

Example case

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ATLAS, Phys. Rev. Lett. 105, 252303

Willian Serenone, et al, arXiv:2102.11919

“lost”: E=57.5 GeV, p=42.5 GeV/c

• assume completely thermalized

​

Landau matching with fluid 🡪 bullet with

• 𝛆 = 30 GeV/V at v_x = 0.7
• R_bullet = 0.5 fm.
• initial position at center of plasma

Movie time

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Willian Serenone, et al, arXiv:2102.11919

From fluid vorticity to hadron polarization

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Back to Back quenched jets

• Back-to-back bullets start at the center
• Two approaches:
• Just add signal from a left-going jet�to the signal from a right-going jet
• Perform a full hydrodynamic evolution �with two “bullets” in the initial condition

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okay, you get the idea…..

these differ

• nonlinear interaction between

smoke rings

Summary

• Hyperon polarization is a sensitive probe of fine substructure of the fluid
• a rare new direction in a mature field
• simultaneously validates (predicted global) and challenges (azimuthal dependence) hydrodynamics
• Important future measurements:
• can we understand collisions at NICA/FAIR in hydrodynamic terms?
• what drives the energy and rapidity dependence of polarization
• unique ring-like structures, first predicted for low root(s), may be observed at highest energies at LHCb
• Toroidal vortex patterns in p+A collisions & jet+QGP
• novel fluid substructure
• characteristic of (all) fluids (with similar initial conditions)
• more compelling test of “tiny droplet” creation
• more compelling test of jet-fluid interaction & sensitive to plasma viscosity
• (in these cases) dominated by velocity gradients 🡪 not affected by “which vorticity is used”
• much more study needed (and underway)
• fluctuating initial conditions, size/energy scan, jet energy dependence
• non-vortical contributions? (Becattini:2021, Fu:2021, Liu:2021)

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Backup

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LOOK AT THE EXPERIMENTS!

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ATLAS, Phys. Lett. B774 (2017) 379

How to estimate “bullet” parameters?

LOOK AT THE EXPERIMENTS!

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ATLAS, Phys. Lett. B774 (2017) 379

How to estimate “bullet” parameters?

LOOK AT THE EXPERIMENTS!

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ATLAS, Phys. Lett. B774 (2017) 379

How to estimate “bullet” parameters?

LOOK AT THE EXPERIMENTS!

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ATLAS, Phys. Rev. Lett. 105, 252303

How to estimate “bullet” parameters?

LOOK AT THE EXPERIMENTS!

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ATLAS, Phys. Rev. Lett. 105, 252303

How to estimate “bullet” parameters?

LOOK AT THE EXPERIMENTS!

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ATLAS, Phys. Rev. Lett. 105, 252303

How to estimate “bullet” parameters?

LANDAU MATCHING PROCEDURE

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LANDAU MATCHING PROCEDURE

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LANDAU MATCHING PROCEDURE

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Effect robust against changes in which vorticity couples to polarization

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Effect robust against changes in which vorticity couples to polarization

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yLfrac = 1.0

yLfrac = 0.0

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yLfrac = 1.0

yLfrac = 0.0

Particlization hypersurface

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W. Serenone, seminar@Dubna 10 march 2021

Back to Back quenched jets

• Energy-momentum deposition on the center: partial quenching of both jets
• Two approaches:
• Superimpose single jet signal
• Perform a full hydrodynamic evolution with two “bullets” in the initial condition
• There are interaction between the two jets, reducing the overall amplitude

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okay, you get the idea…..

Abstract

• Subatomic smoke rings: Polarization and toroidal vorticity in the QGP

​

• Over the past 5 years, there has been intense focus on hyperon polarization in heavy ion collisions, as it is believed to probe the vortical substructure of the fluid created in the collision. Both relativistic hydrodynamics and transport calculations, considered as a coarse-grained fluid, reproduce some experimental observations remarkably well, while they fail at others.
• So far, studies have focused on polarization and vorticity in non-central symmetric (A+A) collisions. I will discuss recent suggestions to study flow fields with quite different structure. The first is that created in central p+A collisions, in which the (assumed) fluid may be initialized with a nontrivial longitudinal flow structure. The second corresponds to a jet locally injecting energy and momentum into the expanding fluid around it. In each case, toroidal vortex structures may result. Using viscous relativistic 3D hydrodynamics, implemented in the MUSIC package, I present calculations of these structures, including quantitative predictions of their manifestation in experiment.

​

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Near-future focus – low energy

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HADES, STAR FXT, NICA, FAIR

UrQMD

• UrQMD Deng, Huang, Ma, Zhang, PRC101, 064908 (2020)
• 3FD Ivanov, Toneev, Soldatov, PRC100, 014908 (2019)
• hydro Csernai, Xie et al, PRC90 021 021904(R) (2014); PRC94 054907 (2016)

​

Fall of (midrapidity) polarization with energy attributed to angular momentum migrating to forward rapidity

​

Is there a peak polarization? Peak vorticity?

Can we “map” the vorticity migration?

​

This energy region is difficult to model, but important.

3FD

Look for STAR Measurement by Joey Adams (RSN)

Speaking of forward rapidity – part 1

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Xie, Wang, Csernei EPJ(2020)80:39

Wei,Deng,Huang PRC99(2019)014905

Wu et al, PRRes1(2019)033058

Liang, et al arXiv:1912.10223

Deng, Huang PRC93(2016)064907

While most models reproduce midrapidity

polarization well, predictions in unexplored

kinematic regions vary significantly

​

Maybe something to be learned by breaking

new ground?

Speaking of forward rapidity – part 2

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Several papers/groups using a variety of models:

• vorticity is dominated by the surface layer between participants & spectators --> importance of forward rapidity
• vortex rings or sheets

Baznat, Gudima, Sorin, Teryaev PRC93, 031902(R) (2016)

“femto-cyclones” on arxiv 🡪 “vortex sheet” in journal ☺

• Helicity separation in heavy-ion collisions (QGSM)�Baznat, Gudima, Sorin, Teryaev PRC88, 061901(R) (2013)
• Vorticity and hydrodynamic helicity in heavy-ion collisions in the HSD model�Teraev & Usubov PRC92 014906 (2015)
• Femto-vortex sheets and hyperon polarization in heavy-ion collisions (QGSM)�Baznat, Gudima, Sorin, Teryaev PRC93, 031902(R) (2016)
• Vorticity in heavy-ion collisions at the JINR Nuclotron-based Ion Collider fAcility (3FD)�Ivanov & Soldatov, PRC 95, 054915 (2017)
• Vortex rings in fragmentation regions in heavy-ion collisions at √sNN = 39 GeV (3FD) �Ivanov & Soldatov PRC97, 044915 (2018)
• Vorticity structure and polarization of Λ hyperons in heavy-ion collisions (PHSD)�Zinchenko, Sorin, Teryaev, Baznat DSPIN-2019 (2020)
• Probing vorticity structure in heavy-ion collisions by local polarization (AMPT)�Xia, Li, Tang, Wang Phys. Rev. C 98, 024905 (2018)

Rings – observable consequences…

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Teraev & Usubov PRC92 014906 (2015)

Zinchenko, Sorin, Teryaev, Baznat DSPIN-2019 (2020)

b=0

In these papers….

• Significant attention to structure in space
• Focus of observable implications seems to center on�convolution with directed flow affecting global polarization

root(s) ~ 5 GeV

Same observations at higher energy

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Ivanov & Soldatov PRC97, 044915 (2018)

Transverse flow should render the vortex rings themselves visible!

root(s) = 39 GeV

• Significant attention to structure in space
• Focus of observable implications seems to center on
• identifying forward rapidity as important
• convolution with directed flow affecting global polarization

Same observations at higher energy

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Ivanov & Soldatov PRC97, 044915 (2018)

Transverse flow should render the vortex rings themselves visible!

root(s) = 39 GeV

• Significant attention to structure in space
• Focus of observable implications seems to center on
• identifying forward rapidity as important
• convolution with directed flow affecting global polarization

root(s) = 200, 2700 GeV

Xia, Li, Tang, Wang Phys. Rev. C 98, 024905 (2018); arxiv:1803.00867

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yLfrac = 1.0

yLfrac = 0.0

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yLfrac = 1.0

yLfrac = 0.0

Sheer velocity field, or density effect?

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UrQMD+hydro Karpenko & Becattini EPJC (2017) 77: 213

Chun Shen, to be published

Azimuthal dependence of global polarization… not understood.

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Karpenko & Becattini EPJC(2017)77:213

Wei, Deng, Huang, PRC99(2019)014905

Hydro

AMPT

Wu, Pang, Huang, Wang

PR Research 1(2019)033058

AMPT+hydro

Use of T-vorticity “works”?

Sign discrepancy

It will be very important for the

experiment to finalize this analysis

In another direction – longitudinal polarization

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(By symmetry, must be quadrupole)

naïve cartoon

+

+

-

-

In another direction – longitudinal polarization

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(By symmetry, must be quadrupole)

naïve cartoon

+

+

-

-

In another direction – longitudinal polarization

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hydro: Becattini & Karpenko, PRL.120.012302 (2018)

AMPT: Xia, Li, Tang, Wang, PRC98.024905 (2018)

In another direction – longitudinal polarization

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hydro: Becattini & Karpenko, PRL.120.012302 (2018)

+

+

-

-

AMPT: Xia, Li, Tang, Wang, PRC98.024905 (2018)

PICR hydro: Xie, Wang, Csernai EPJ80(2019)39

Chiral kinetic: Sun & Ko PRC99(2019)011903(R)

Sign agrees ☺

Sign disagrees ☹

In another direction – longitudinal polarization

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hydro: Becattini & Karpenko, PRL.120.012302 (2018)

+

+

-

-

AMPT: Xia, Li, Tang, Wang, PRC98.024905 (2018)

PICR hydro: Xie, Wang, Csernai EPJ80(2019)39

Chiral kinetic: Sun & Ko PRC99(2019)011903(R)

Sign agrees ☺

Sign disagrees ☹

T-vorticity “works”?

AMPT+hydro Wu, Pang, Huang, Wang PR Res 1(2019)033058

In another direction – longitudinal polarization

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hydro: Becattini & Karpenko, PRL.120.012302 (2018)

+

+

-

-

AMPT: Xia, Li, Tang, Wang, PRC98.024905 (2018)

PICR hydro: Xie, Wang, Csernai EPJ80(2019)39

Chiral kinetic: Sun & Ko PRC99(2019)011903(R)

Sign agrees ☺

Sign disagrees ☹

T-vorticity “works”?

AMPT+hydro Wu, Pang, Huang, Wang PR Res 1(2019)033058

​

Expect new results from LHC!

​

Experiment has given theory plenty to work on.

​

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