The Future of Heavy Flavor and Exotic Hadron Production in RHIC and LHC

Xiaojun Yao MIT

Snowmass Energy Frontier Preparatory Joint Topical Group Sessions

July 8, 2020 Quarkonium Production: Factorization J/ψ Factorization in proton proton collision c

c¯

p+p H+X i+j (QQ¯) +X ! = f f ! n i ⌦ j ⌦ hOni proton PDF short-distance production long-distance matrix element: of heavy quark pair evolution of pair into quarkonium universal

QGP effects: dissociation, Heavy ion nuclear PDF (re)combination, energy loss etc In heavy ion, try to understand modifications from nuclear mediums

Test universality of LDME in high multi p-p X.Dong July 1 9:50 am

!2 Recent Theoretical Insights from Open System

In vacuum, quarkonium described by Schrödinger equation

@ 2 i (r)= r + V (r) (r) @t M h i 1.0 Start with 1S, closed system 1S probability is conserved 0.8

0.6 1S wavefunction (t = 0) = 1S | i | i 0.4 1S (t) 2 =1 |h | i| 0.2

0.0 0.0 0.5 1.0 1.5 2.0 r

!3 Recent Theoretical Insights from Open System

In QGP, quarkonium described by stochastic Schrödinger equation

@ 2 i (r)= r + V (r) (r) + i(r)+⇠(r, t) (r) @t M h i h i 1.0 Start with 1S, open system 1S probability NOT conserved 0.8 Stochastic forces —> wavefunction decoherence (t = 0) = 1S 0.6 | i | i 1S (t) 2 < 1 0.4 |h | i| 0.2 Dissociation of 1S 2 0.0 2S (t) > 0 if 2S exists 0.0 0.5 1.0 1.5 2.0 |h | i| r Recombination of 2S ! Correlated/uncorrelated recombination: from correlated pair from same/differential initial hard vertices !4 Upsilon in 5020 GeV PbPb Collision

with cross-talk (correlated) recombination without cross-talk recombination

1S theory 2S syst 1S w/o cross recombination 1.0 1S syst 2S stat 1.0 1S syst 1S stat 3S theory 1S stat 2S theory 3S 95% CL 0.8 2S w/o cross recombination 0.8 2S syst 2S stat 0.6 0.6 3S w/o cross recombination

AA AA 3S 95% CL R R 0.4 0.4

0.2 0.2

0.0 0.0 0 100 200 300 400 0 100 200 300 400 Npart Npart

Nuclear PDF needs better constrained

CMS arXiv:1805.09215 X.Yao, W.Ke, Y.Xu, S.A.Bass, B.Müller, arXiv:2004.06746 !5 Experimental Evidence of Correlated Recombination

with cross-talk (correlated) recombination without cross-talk recombination

2S 2S w/o cross recombination 1.0 1P 1P w/o cross recombination

0.8 0.4

0.6 AA AA R R 0.4 0.2

0.2

0.0 0.0 0 100 200 300 400 0 100 200 300 400 Npart Npart Dissociation rate of 1P ~ dissociation rate of 2S, due to similar binding energy/size

In medium, P(1P—>2S) ~ P(2S—>1P), via dissociation and correlated recombination

But more 1P states produced initially than 2S, so more 2S regenerated than 1P

!6 Experimental Evidence of Correlated Recombination

1.0 w/ cross recombination

0.8 ) ) S P (2 (1 0.6 AA AA R R 0.4

0.2 0 5 10 15 20 pT (GeV)

Importance of correlated recombination can be checked at RHIC and LHC

For RHIC, need to distinguish between 2S and 3S, sPHENIX J. Huang, July 1 10:05 am

!7 X(3872): Structure

PC ++ J =1 mX = mD0 + mD¯ 0 0.3 MeV ⇤ ±

ccq¯ q¯ D D*

tetraquark molecule

Br[D0D¯ 0⇡0] > 0.4 Anything that can mix in quantum mechanics will mix 0 ¯ 0 Br[D D⇤ ] > 0.3 Must have large overlap with molecule wavefunction Br[J/ + ] > 0.055 ···

!8 X(3872): Production

Any calculation needs to explain these simultaneously

mX = mD0 + m ¯ 0 0.3 MeV D⇤ ± Hard to be produced in QGP phase

Interactions during the hadronic gas phase: dissociation v.s. (re)combination

Determining its structure needs interplay between theory and experiment Interesting to measure it in p-A collisions, also at low pT in A-A collisions

!9 Doubly Charmed Baryon

++ • LHCb observed a new baryon ⌅ cc (ccu): u bound around cc core LHCb, Phys. Rev. Lett. 119, no.11,112001 (2017) • Pair of heavy Q in anti-triplet forms bound state (diquark)

QQ anti-triplet c Q Q ¯ singlet c color neutral colored c¯ exist in vacuum not exist in vacuum c exist in QGP J/ cc diquark (1S) • Heavy diquark in QGP: dissociation, recombination (similar to quarkonium), carry color, energy loss different from quarkonium • Hadronize into doubly charmed baryon • Can help to test recombination as production mechanism

!10 Doubly Charmed Baryon Production in Heavy Ion Collisions

++ XY, B.Mueller, Phys.Rev.D97 Predicted production rate of ⌅cc 0.5 (2018) no.7, 074003 in 2760 GeV PbPb, -1

0.1 Compare: c quark rate ~10 per collision 0.0 0 1 2 3 4 5 pT (GeV)

Production rate from initial hard collision probably small Study recombination from measurements

!11 Doubly Heavy Tetraquark Production in Heavy Ion

Same calculation can be extended to study doubly heavy tetraquark (bound state) Only difference: at hadronization coalescence with two light quarks v.s. one

Heavy quark diquark symmetry

Hadronization of doubly heavy baryon similar to hadronization of singly heavy meson

Hadronization of doubly heavy tetraquark similar to hadronization of singly heavy baryon

Enhancement of singly heavy baryon Expect enhancement of observed in heavy ion/high multi p-p doubly heavy tetraquark G. M. Innocenti July 1 9:05 am

Heavy ion collision may be a good place to search for doubly heavy tetraquarks

!12 Summary

• Quarkonium production:

• Test universality of LDME and factorization in high multi p-p collisions

• Correlated recombination motivated from open quantum system; experimental signal: Raa(1P)/Raa(2S) for bottomonium

• Exotic hadrons:

• X(3872): more measurements help understand its structure

• Doubly heavy baryon/tetraquark, (re)combination, heavy quark diquark symmetry, enhanced production—>search for these tetraquarks in heavy ion

• Fragmentation in heavy-flavor jets: universal in ee, pp, pA? Lambda_c v.s D !13 Coupled Transport Equations of Heavy Flavors

open heavy quark antiquark

@ + ( + x˙ + x˙ ¯ )f ¯ (x , p , x ¯ , p ¯ ,t)= ¯ + @t Q · rxQ Q · rxQ¯ QQ Q Q Q Q CQQ CQQ¯ CQQ¯ each quarkonium state @ + ( + x˙ x)fnls(x, p,t)= nl = 1S, 2S,1P etc. @t · r Cnls Cnls b B¯ b hadronization b 1S 1S diffuse b ¯ ¯b propagate b ¯b hadronization ¯b B

initial QGP medium expands and cools hadron gas production

time !14 Coupled Transport Equations of Heavy Flavors

open heavy quark antiquark

@ + ( + x˙ + x˙ ¯ )f ¯ (x , p , x ¯ , p ¯ ,t)= ¯ + @t Q · rxQ Q · rxQ¯ QQ Q Q Q Q CQQ CQQ¯ CQQ¯ each quarkonium state @ + ( + x˙ x)fnls(x, p,t)= nl = 1S, 2S,1P etc. @t · r Cnls Cnls recombine if b T < melting T b b 1S 1S nL nL b ¯ ¯ b ¯b b 1S,2S,1P… ¯b ¯b nL nL b b from other open b initial QGP medium expands and cools hadron gas production

time !15 Coupled Transport Equations of Heavy Flavors

open heavy quark antiquark

@ + ( + x˙ + x˙ ¯ )f ¯ (x , p , x ¯ , p ¯ ,t)= ¯ + @t Q · rxQ Q · rxQ¯ QQ Q Q Q Q CQQ CQQ¯ CQQ¯ each quarkonium state @ + ( + x˙ x)fnls(x, p,t)= nl = 1S, 2S,1P etc. @t · r Cnls Cnls b correlated recombination b b 1S 1S nL nL b ¯ ¯ b ¯b b 1S,2S,1P… ¯b ¯b nL nL b b from other open b

uncorrelated recombination

!16