[PPT] - Heavy Flavour Hadronisation in Pythia Peter Skands (Monash PowerPoint Presentation

SLIDE 1

VINCIA VINCIA

Heavy Flavour Hadronisation in Pythia

Peter Skands (Monash University)

Heavy-Flavour Hadronization in pp & HI Collisions, CERN, March 2020

1. Heavy-Flavour Hadronisation in the Lund Model
2. Constraints
3. From ee to pp
4. New Theory Models in Pythia
5. Some Suggestions for New Measurements
6. Multiply heavy hadrons?

SLIDE 2

Reminder: Fragmentation Models

Peter Skands

2

Monash U.

๏Hard process (e.g., dijets) ➤ hard factorisation scale QUV ~ pTjet ๏Parton Showers: perturbative bremsstrahlung down to QIR ~ 1 GeV ๏Hadronisation: confinement (+ hadron decays) at QHAD ~ QIR

u(~ p⊥0, p+) d ¯ d s¯ s ⇡+(~ p⊥0 − ~ p⊥1, z1p+) K0(~ p⊥1 − ~ p⊥2, z2(1 − z1)p+) ... QIR shower · · · QUV

Perturbative main parameter αs

Different “tunes” use different αseff(mZ) values Monash : 0.1365 A14: 0.129

Non-Perturbative Fragmentation Function (at QHAD)

๏Spectrum = combination of αs choice & non-perturbative parameters

+ flavour / pT / … parameters, hadron decay tables

SLIDE 3

Flavour Composition in the Lund Model

Peter Skands

3

Monash U.

๏Starting point: isolated string in 1+1 dimensions

Tension κ ~ 1 GeV/fm ~ 0.2 GeV2
String breaks by Schwinger mechanism

๏+ Spin-splitting in hadron multiplets V/P ≠ 3 ๏

Schwinger Tunneling M a s s l e s s e n d p

i

n t M a s s l e s s e n d p

i

n t

t x mq

➜ Suppression of strange

quarks (and diquarks)

➜ StringFlav:probStoUD = 0.217

exp −m2

q + p2 ⊥

κ !

<latexit sha1_base64="aAal5nrmGpvCXvPlbYJdVuONyw=">ACG3icdVDBTtAEF1TSkMoENpjLysiJCqEZRuIk1skLj1SiQBSHKz1Zpysra3u2PUyMp/9NJf6aUHqopTpR76N2xCKrUInjTS03szmpmXKCkMet4fZ+XF6su1V7X1+sbrza3txs6bC1OUmkOPF7LQVwkzIEUOPRQo4UpYFki4TKZnM79yxvQRhT5OU4VDI2ykUqOEMrxY0gs8qkpDi/mGUasarLP50HdADquJIgVbXwayKJkwpNou0GI3xfdxoem4YdLz2CfVcr9UJ/XBOjsJWq0N91ugSZY4ixu/omHBywxy5JIZ0/c9hYOKaRcwqwelQYU4xM2gr6lOcvADKrFbzO6Z5UhTQtK0e6UP+dqFhmzDRLbGfGcGwe3PxKa9fYtoeVCJXJULOHxalpaRY0HlQdCg0cJRTSxjXwt5K+ZjZhNDGWbch/P2UPk8uAtc/dk8+Hje7WUcNfKO7J94pOQdMkHckZ6hJMv5Bu5JT+cr85356dz9C64ixn3pL/4Py+B07AoZw=</latexit>

ρ/π StringFlav:mesonUDvector = 0.50 K*/K StringFlav:mesonSvector = 0.55 D*/D StringFlav:mesonCvector = 0.88 B*/B StringFlav:mesonBvector = 2.2

Note: model parameters are for primary hadrons ≠ measured ratios (feed-down)

mq

SLIDE 4

Flavour Composition in the Lund Model

Peter Skands

4

Monash U.

๏Starting point: isolated string in 1+1 dimensions

Tension κ ~ 1 GeV/fm ~ 0.2 GeV2
String breaks by Schwinger mechanism

๏+ Spin-splitting in hadron multiplets V/P ≠ 3 ๏

Schwinger Tunneling M a s s l e s s e n d p

i

n t M a s s l e s s e n d p

i

n t

t x mq

➜ Suppression of strange

quarks (and diquarks)

➜ StringFlav:probStoUD = 0.217

exp −m2

q + p2 ⊥

κ !

<latexit sha1_base64="aAal5nrmGpvCXvPlbYJdVuONyw=">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</latexit>

ρ/π StringFlav:mesonUDvector = 0.50 K*/K StringFlav:mesonSvector = 0.55 D*/D StringFlav:mesonCvector = 0.88 B*/B StringFlav:mesonBvector = 2.2

Note: model parameters are for primary hadrons ≠ measured ratios (feed-down)

Rookie Mistake: for D*/D in the Monash tune

I took the D and D* rates from separate sources ➤ wrong ratio Should be higher ~ 1.25 - 1.5 to agree with measured values

Thanks to D. Bardhan for pointing to this

mq

๏arXiv:1404.5630

SLIDE 5

Heavy-Flavour Endpoint Quarks

Peter Skands

5

Monash U.

๏Same starting point as for massless endpoints

Tension κ ~ 1 GeV/fm ~ 0.2 GeV2
String breaks by Schwinger mechanism
Same parameters govern Ds/D, Bs/B, Λc/D, Λb/B ➜ Interesting to check if

Ds/D, Bs/B affected in same way in same environments where we see strangeness enhancements in light-quark sector: multiplicity dependence

๏Massive endpoints have v < c ➜ smaller string space-time area:

➜ Modified (“Lund-Bowler”) FF:
Schwinger

Tunneling

t x mq mq

➜ Suppression of strange

quarks (and diquarks)

➜ StringFlav:probStoUD = 0.217

exp −m2

q + p2 ⊥

κ !

<latexit sha1_base64="aAal5nrmGpvCXvPlbYJdVuONyw=">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</latexit>

!

(1 − z)a z1 + rQ b m2

Q exp

−b m2

⊥,h

z !

<latexit sha1_base64="oCsGDCyEfHJKje51M5XeY3UoRIY=">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</latexit>

Massive endpoint

mQ mQ

Massive endpoint

(Note: Peterson etc strictly speaking

incompatible with causality in string picture)

๏

with rb~rc~1

StringZ:rFactB = 0.855

SLIDE 6

Constraints : B Spectra

Peter Skands

6

Monash U.

๏Main constraint: xB spectra of weakly decaying B hadrons in Z decays

2 −

10

1 −

10 1

f(x) dx

N-1

x

∫

(moments)

weak B

x

8.301 Pythia Data from Eur. Phys. J. C71 (2011) 1557

LEP (combined) 0.855) ≡

B

(r Monash 1) →

B

(r Monash 4C Vincia GeV 91.2 q q → Z

5 10 15 20

Mellin Moment N 0.8 0.9 1 1.1 1.2 Theory/Data

1 −

10 1 10

B

1/N dN/dx

(DELPHI)

weak B

x

8.301 Pythia Data from Eur.Phys.J. C71 (2011) 1557

DELPHI 0.855) ≡

B

(r Monash 1) →

B

(r Monash 4C Vincia GeV 91.2 q q → Z

0.2 0.4 0.6 0.8 1

x 0.6 0.8 1 1.2 1.4 Theory/Data

Spectrum Moments

๏for details see arXiv:1404.5630 (section 2.3)

SLIDE 7

+ B-tagged Event Shapes & Jet Rates

Peter Skands

7

Monash U.

๏IR safe: sensitive to αs and b mass effects in shower + hadronisation ๏for details see arXiv:1404.5630 (section 2.3)

0.9 1 1.1

R3bl

8.301 Pythia Data from Eur.Phys.J.C46(2006)569

Delphi 0.855) ≡

B

(r Monash 1) →

B

(r Monash 4C Vincia GeV 91.2 q q → Z

0.02 0.04

23

y 0.9 0.95 1 1.05 1.1 Theory/Data

3-jet rate (b/udsc) Durham kT 3-jet resolution y23

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10

W

/dB σ d σ 1/

Wide Jet Broadening (b)

8.301 Pythia Data from Phys.Rept. 399 (2004) 71

L3 0.855) ≡

B

(r Monash 1 ≡

B

r Monash 4C Vincia GeV 91.2 q q → Z

0.1 0.2 0.3

(b)

W

B 0.6 0.8 1 1.2 1.4 Theory/Data

Jet Broadening (b)

SLIDE 8

LHC: Top Decays ➤ In-situ controlled B-Jet Sample?

Peter Skands

8

Monash U.

๏Yesterday: 25th anniversary of the top quark discovery

March 2nd 1995 t→bW provides a clean high-statistics reference sample, with a well- defined initial b-quark energy (in top CM) very similar to Z → bb. Compare B FF(x) and B hadron flavour ratios to those for inclusive b-jets,

incl. any dependence on UE level (measured away from the top jets)

Note: finite top width ➜ “collective effects” may be suppressed in top

(“early” vs “late” resonance decays)

SLIDE 9

Some Comments on b fragmentation “tuning”

Peter Skands

9

Monash U.

๏Note: Monash uses “large" TimeShower:alphaSvalue = 0.1365

Regarded at least in part as making up for NLO K-factor for ee→3 jets

(baseline Pythia only accurate to LO for 3 jets).

Consistent with 3-flavour ΛQCD ~ 0.35 GeV (since we use 1-loop running)

๏Not guaranteed to be universal.

LHC studies tend to prefer lower effective values of αs
E.g., A14 uses TimeShower:alphaSvalue = 0.129 (could be reinterpreted via

CMW to MSbar alphaS(mZ) ~ 0.12 so consistent with world average.)

(but I would then also change to 2-loop running to preserve ΛQCD value)

๏E.g., a lower αs ➜ less perturbative radiation ➜ harder xb(QIR)

➜ Would need to retune non-perturbative parameters (e.g., rb) at LEP
Problem: most LEP measurements are inclusive (including 3-jet events)

๏

➜ Would need 3-jet NLO merging to ensure correct 3-jet admixture.

SLIDE 10 ๏No “C-tagged” data from LEP (that I am aware of)

Monash tune only used a single D* spectrum (ALEPH) ➜ rc

/dx

D

> dn

D

1/<n

0.5 1 1.5 2 2.5 >0.1)

E

) (x

± *

x(D

Pythia 8.183 Data from Eur.Phys.J. C16 (2000) 597

ALEPH PY8 (Monash) PY8 (Default) PY8 (Fischer)

bins

/N

2 5%

χ 0.1 ± 1.4 0.2 ± 2.8 0.2 ± 3.2

V I N C I A R O O T E

x

0.2 0.4 0.6 0.8 1

Theory/Data 0.6 0.8 1 1.2 1.4

Constraints : Charm

Peter Skands

10

Monash U.

(4C)

0.2 0.4 0.6 0.8 1

E

x 0.2 0.4 0.6 0.8 1 Ratio

xE (D*) spectrum Born Process

Actual charm fragmentation not seen very clearly. For x<0.5, the inclusive D* spectrum is dominated by B decays cc → Z bb → Z uu+dd+ss Z

SLIDE 11

From ee to pp: multiple parton interactions (MPI)

Peter Skands

11

Monash U.

Rapidity Nch d e n s i t y g r

w

s l i n e a r l y w i t h NMPI

Simple, clean, factorized picture …

Leading NC: each parton-parton interaction scatters ‘new’ colours → incoherent addition of colours 1 or 2 strings per MPI

SLIDE 12

Anticipated already in first Pythia MPI model (Sjöstrand & van Zijl, 1987) Tevatron <Nch> and <ΣpT> in “Transverse” UE region Required ~ 100% CR (Rick Field, “Tune A”, 2002) “CR” parameter = probability for MPI to just generate “kinks” on hard-process colour structure, rather than new strings of their own

!

WRONG!

+ Many new measurements and discoveries from LHC (& RHIC)

(e.g., CMS ridge, ALICE strangeness vs Nch, …) ➤ Not a small effect, then …

SLIDE 13

The MPI are all within a proton radius of each other (in pp)

Peter Skands

13

Monash U.

Rapidity Colour Ropes? QGP? SU(3) Coherence Colour Reconnections? String-String potentials & interactions?

Fertile ground for model building

Hadron rescatterings?

The picture today

Nch d e n s i t y s t i l l m a i n i n d i c a t

r
f

< nMPI >

SLIDE 14

Brief Summary of “New” Theory Models in Pythia

Peter Skands

14

Monash U.

๏QCD-inspired CR

Stochastically sample subleading-NC connections according to SU(3) weights and

choose among possibilities (incl colour-ϵ ones) based on string-length minimisation.

➤ some flow effects & additional baryons (incl multiply-heavy); no extra strangeness

๏Ropes & Shoving

Ropes: allow QCD charges to combine into higher representations: 6, 10, 15, 21, 28, …

with higher string tensions (Casimir scaling) ➤ more strangeness & more baryons

Shoving: explicit dynamical model of repulsion between different strings/ropes ➤ flow

๏Thermodynamical String fragmentation ๏+ Much ongoing work …

Hadronic Rescattering (Sjöstrand+Utheim)
HI extensions (Angantyr, PISTA) & extensions with UrQMD (Bierlich et al.)
Interacting Strings: momentum-space alternative to ropes+shoving (Duncan+Skands)
Back to basics: fragmentation of a single string: early / out-of-equilibrium, and thermal
effects. Time-varying string tension out soon. + other variants? E.g., UCLA model?

Christiansen, Skands, JHEP 1508 (2015) 003 Bierlich, Gustafson, Lönnblad, Tarasov, JHEP 1503 (2015) 148 Bierlich, Gustafson, Lönnblad, PLB 779 (2018) 58 Fischer, Sjöstrand, JHEP 1701 (2017) 140 ColourReconnection:mode = 1

SLIDE 15

Some Suggestions for New Measurements

Peter Skands

15

Monash U.

๏Want to disentangle <pT>, <strangeness>, <baryons>, <Nch>

E.g., CR and “flow” increase <pT> without (directly) affecting <ϛ>
“Baryonic” CR can increase <ℬ>
Higher tensions/temperatures: correlated <pT>, <ϛ>, and <ℬ>

๏Some Simple Questions:

How local are the <ϛ> and <ℬ> enhancement mechanisms?

๏

How far in phase space is nearest anti-strange / anti-baryon?

๏

For different values of Nch density, pTB or pT(b-jet), and ϛ density

๏

E.g., heavy-flavour tag, say Bs ➤ know the endpoint flavour ➤ look for nearest anti-strange quark.

๏

What is the distance in pT? in rapidity (along z / along b-jet)? in ΔR?

How do the HF fractions depend on event multiplicity?
<ϛ>
<ℬ>
(\varsigma)

SLIDE 16

Heavy-Flavour Baryons

Peter Skands

16

Monash U.

๏Example: QCD-inspired CR

Allows “junction reconnections”, e.g.:

๏Generically expect dependence on

multiplicity ➤ Measure <B/M>(Nch) ?

(Should be true for ropes, hydro, … too)
+ baryon-antibaryon rapidity dependence?

·

−

·

−

5.3 · 10−2 6.5 · 10−2 1.2 · 10−2 6.6 · 10−3 1.3 · 10−2 5.4 · 10−4 1.5 · 10−2 5.2 · 10−4 1.3 · 10−2 5.1 · 10−4 2.2 · 10−3 9.5 · 10−4 2.4 · 10−3 9.4 · 10−4 2.2 · 10−3 9.1 · 10−4 2.1 · 10−4 1.0 · 10−7 1.6 · 10−3 2.3 · 10−3 8.2 · 10−4 3.9 · 10−4 9.5 · 10−4 3.1 · 10−5 1.0 · 10−3 3.7 · 10−5 9.4 · 10−4 3.2 · 10−5 9.5 · 10−4 3.1 · 10−5 1.0 · 10−3 3.7 · 10−5 9.4 · 10−4 3.2 · 10−5 1.8 · 10−5 1.1 · 10−6 Npar/Nevents (all) 2.4 · 101

ColourReconnection:mode = 1 = 0 Christiansen, Skands, JHEP 1508 (2015) 003

−

D+ Λ+

c

Σ++

c

Σ+

c

Σ0

c

Σ∗++

c

Σ∗+

c

Σ∗0

c

ccq7 B+ Λ0

b

Σ+

b

Σ0

b

Σ−

b

Σ∗+

b

Σ∗0

b

Σ∗−

b

bcq7 bbq7 Particle

q ¯ q ¯ q q ¯ q q ¯ q q J ¯ J

(b) Type II: junction-style reconnection

For the parameters used in that study, Λc/D+ increased by factor 2 Λb/B+ by factor 3 + potentially larger changes for Σc,b(*)

SLIDE 17

Heavy-Flavour Baryons

Peter Skands

17

Monash U.

๏Example: QCD-inspired CR

Allows “junction reconnections”, e.g.:

๏Generically expect dependence on

multiplicity ➤ Measure <B/M>(Nch) ?

(Should be true for ropes, hydro, … too)
+ baryon-antibaryon rapidity dependence?

·

−

·

−

5.3 · 10−2 6.5 · 10−2 1.2 · 10−2 6.6 · 10−3 1.3 · 10−2 5.4 · 10−4 1.5 · 10−2 5.2 · 10−4 1.3 · 10−2 5.1 · 10−4 2.2 · 10−3 9.5 · 10−4 2.4 · 10−3 9.4 · 10−4 2.2 · 10−3 9.1 · 10−4 2.1 · 10−4 1.0 · 10−7 1.6 · 10−3 2.3 · 10−3 8.2 · 10−4 3.9 · 10−4 9.5 · 10−4 3.1 · 10−5 1.0 · 10−3 3.7 · 10−5 9.4 · 10−4 3.2 · 10−5 9.5 · 10−4 3.1 · 10−5 1.0 · 10−3 3.7 · 10−5 9.4 · 10−4 3.2 · 10−5 1.8 · 10−5 1.1 · 10−6 Npar/Nevents (all) 2.4 · 101

ColourReconnection:mode = 1 = 0 Christiansen, Skands, JHEP 1508 (2015) 003

−

D+ Λ+

c

Σ++

c

Σ+

c

Σ0

c

Σ∗++

c

Σ∗+

c

Σ∗0

c

ccq7 B+ Λ0

b

Σ+

b

Σ0

b

Σ−

b

Σ∗+

b

Σ∗0

b

Σ∗−

b

bcq7 bbq7 Particle

q ¯ q ¯ q q ¯ q q ¯ q q J ¯ J

(b) Type II: junction-style reconnection

For the parameters used in that study, Λc/D+ increased by factor 2 Λb/B+ by factor 3 + potentially larger changes for Σc,b(*)

QM2018

Qu

S. Plumari, yesterday

Also: CMS 1906.03322

f

/(f +f ) is observed to depend on p

arXiv:1902.06794

fs fu + fd ∝ ncorr( ¯ B0

s)

ncorr( ¯ B0) + ncorr(B−)

B. Audurier, yesterday

SLIDE 18

Heavy-Flavour Baryons

Peter Skands

18

Monash U.

๏Example: QCD-inspired CR

Allows “junction reconnections”, e.g.:

๏Generically expect dependence on

multiplicity ➤ Measure <B/M>(Nch) ?

(Should be true for ropes, hydro, … too)
+ baryon-antibaryon rapidity dependence?

·

−

·

−

5.3 · 10−2 6.5 · 10−2 1.2 · 10−2 6.6 · 10−3 1.3 · 10−2 5.4 · 10−4 1.5 · 10−2 5.2 · 10−4 1.3 · 10−2 5.1 · 10−4 2.2 · 10−3 9.5 · 10−4 2.4 · 10−3 9.4 · 10−4 2.2 · 10−3 9.1 · 10−4 2.1 · 10−4 1.0 · 10−7 1.6 · 10−3 2.3 · 10−3 8.2 · 10−4 3.9 · 10−4 9.5 · 10−4 3.1 · 10−5 1.0 · 10−3 3.7 · 10−5 9.4 · 10−4 3.2 · 10−5 9.5 · 10−4 3.1 · 10−5 1.0 · 10−3 3.7 · 10−5 9.4 · 10−4 3.2 · 10−5 1.8 · 10−5 1.1 · 10−6 Npar/Nevents (all) 2.4 · 101

ColourReconnection:mode = 1 = 0 Christiansen, Skands, JHEP 1508 (2015) 003

−

D+ Λ+

c

Σ++

c

Σ+

c

Σ0

c

Σ∗++

c

Σ∗+

c

Σ∗0

c

ccq7 B+ Λ0

b

Σ+

b

Σ0

b

Σ−

b

Σ∗+

b

Σ∗0

b

Σ∗−

b

bcq7 bbq7 Particle

q ¯ q ¯ q q ¯ q q ¯ q q J ¯ J

(b) Type II: junction-style reconnection

For the parameters used in that study, Λc/D+ increased by factor 2 Λb/B+ by factor 3 + potentially larger changes for Σc,b(*)

First step, e.g., ALICE D meson associated track multiplicities in arXiv:1910.14403

QM2018

Qu

From S. Plumari, yesterday

Also: CMS 1906.03322

SLIDE 19

(Some) LHCb measurements

Peter Skands

19

Monash U.

๏Bs/B+ vs event kinematics

From Bs → J/ψ φ & B+ → J/ψ K+
No dependence on pLB, ηB
Decreasing trend with pTB
Would be highly interesting to

see vs event multiplicity / associated track multiplicity

๏Ds asymmetry (S. Klaver, Moriond 2018)

Strong pT dependence in Pythia,

not seen in data

๏

High pT ➤ Coherence effect?

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) = σ(pp → D+

s ) − σ(pp → D− s )

σ(pp → D+

s ) + σ(pp → D− s )

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] c [GeV/

B T

p

10 20 30 40

d

f

/

s

f

0.24 0.26 0.28 0.3 ) σ 1 ± LHCb average ( Distribution mean

B T

p

k

e

∝

)

B T

p

( f

LHCb

(a) f

/

f

5 10 15 20 25

] c [GeV/

T

p

2.5 − 2 − 1.5 − 1 − 0.5 − 0.5 1 1.5 2 2.5

[%] )

+ s

D (

P

A

Pythia 8.1 LHCb = 7-8 TeV s < 3.0 y 2.0 <

preliminary

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SLIDE 20

Multiply Heavy Hadrons?

Peter Skands

20

Monash U.

๏Heavy flavours produced

perturbatively, not in string/cluster breakups;

So why would multiply heavy

hadrons be interesting as soft probes?

Because they also probe the

confinement field in unique ways (colour-ϵijk)

๏E.g., the Ξcc has been

measured

Does its rate vary with

associated track density?

−

·

−

·

−

·

−

·

−

D+ 5.3 · 10−2 5.3 · 10−2 6.5 · 10−2 Λ+

c

4.0 · 10−3 7.9 · 10−3 1.2 · 10−2 6.6 · 10−3 Σ++

c

2.7 · 10−4 1.3 · 10−2 1.3 · 10−2 5.4 · 10−4 Σ+

c

2.5 · 10−4 1.5 · 10−2 1.5 · 10−2 5.2 · 10−4 Σ0

c

2.5 · 10−4 1.3 · 10−2 1.3 · 10−2 5.1 · 10−4 Σ∗++

c

5.1 · 10−4 1.7 · 10−3 2.2 · 10−3 9.5 · 10−4 Σ∗+

c

4.9 · 10−4 1.9 · 10−3 2.4 · 10−3 9.4 · 10−4 Σ∗0

c

4.8 · 10−4 1.7 · 10−3 2.2 · 10−3 9.1 · 10−4 ccq7 2.1 · 10−4 2.1 · 10−4 1.0 · 10−7 B+ 1.6 · 10−3 1.6 · 10−3 2.3 · 10−3 Λ0

b

1.9 · 10−4 6.3 · 10−4 8.2 · 10−4 3.9 · 10−4 Σ+

b

1.1 · 10−5 9.3 · 10−4 9.5 · 10−4 3.1 · 10−5 Σ0

b

1.2 · 10−5 1.0 · 10−3 1.0 · 10−3 3.7 · 10−5 Σ−

b

1.1 · 10−5 9.3 · 10−4 9.4 · 10−4 3.2 · 10−5 Σ∗+

b

1.1 · 10−5 9.3 · 10−4 9.5 · 10−4 3.1 · 10−5 Σ∗0

b

1.2 · 10−5 1.0 · 10−3 1.0 · 10−3 3.7 · 10−5 Σ∗−

b

1.1 · 10−5 9.3 · 10−4 9.4 · 10−4 3.2 · 10−5 bcq7 1.8 · 10−5 1.8 · 10−5 bbq7 1.1 · 10−6 1.1 · 10−6 Particle New CR model (Npar/Nevents) Old CR model string junction all Npar/Nevents (all) π+ 2.5 · 101 2.5 · 101 2.4 · 101

ColourReconnection:mode = 1 = 0 Christiansen, Skands, JHEP 1508 (2015) 003

Note: the baryon “predictions” depend on poorly constrained model parameters; highlight measurement sensitivity

LHCb-PAPER-2019-037

SLIDE 21

To discuss: observables to tell apart …

Peter Skands

21

Monash U.

๏CR: longitudinal (1D) strings + transverse boosts: flow-like effects

No <ϛ> enhancement; low velocity dispersions relative to common boosts
Additional tracers: multiply heavy baryons (will at least ➤ constraints!)

๏Ropes etc: longitudinal (1D) strings with higher effective tensions

Strangeness enhancement + higher <pT>, but still “1D”
➤ rank ordering, const dN/dy?

๏Shoving etc.: Longitudinal strings with transverse repulsions

1D “rank” still relevant for <ℬ>, <ϛ>, and (local) pT conservation ➤

correlations?

+ higher tensions? Is <pT> correlated or anti-correlated with <ϛ>, <ℬ> ?

๏Thermal/Statistical systems: 3D systems with higher effective T

Very high dispersions, 3D.
Quantum number and pT conservation not ordered in “rank” at all?

SLIDE 22

Extra Slides

SLIDE 23

What a strange world we live in, said Alice [to the queen of hearts]

P E T ER SK A ND S

23

๏We wanted to know if “violent” collision

events produced higher-strength fields.

๏Smoking gun would be a higher fraction

f strange particles being produced
(higher-strength fields ⟹ more energy per

“space-time volume” ⟹ easier to produce higher-mass quark-antiquark pairs)

๏Jackpot!

D.D. Chinellato – 38th International Conference on High Energy Physics

Strangeness 1 Strangeness 1 Strangeness 2 Strangeness 3

D.D. Chinellato – 38th International Conference on High

|< 0.5 η |

〉 η /d

ch

N d 〈

10

2

10

3

10

)

+

π +

−

π Ratio of yields to (

3 −

10

2 −

10

1 −

10

16) × (

+

Ω +

−

Ω 6) × (

+

Ξ +

−

Ξ 2) × ( Λ + Λ

S

2K ALICE = 7 TeV s pp, = 5.02 TeV

NN

s p-Pb, = 2.76 TeV

NN

s Pb-Pb,

PYTHIA8 DIPSY EPOS LHC ALICE, arXiv:1606.07424

S

2K 2) × ( Λ + Λ 6) × (

+

Ξ +

−

Ξ 16) × (

+

Ω +

−

Ω [1] [2] [3]

Now working on models in which nearby

fragmenting fields interact with each other.

Interactions between QCD strings!
Higher tensions + repulsion effects ➤

modifications in high-density environments

(Competing idea: the whole thing turns into

a near-perfect liquid which gets heated up.)

SLIDE 24

D meson associated tracks (ALICE)

Peter Skands

24

Monash U.

ALICE

*+

, D

+

, D Average D

c > 0.3 GeV/

assoc T

p c < 5 GeV/

D T

p 3 <

)

1

baseline (rad − ϕ ∆ d

assoc

N d

D

N 1

1 2 3 4 5

scale uncertainty

4% − 4% +

| < 1 η ∆ | < 0.5, |

cms D

y | = 5.02 TeV

NN

s pp, c > 0.3 GeV/

assoc T

p c < 8 GeV/

D T

p 5 < scale uncertainty

4% − 4% +

PYTHIA6, Perugia 2011 PYTHIA8, Tune 4C HERWIG 7 c > 0.3 GeV/

assoc T

p c < 16 GeV/

D T

p 8 < scale uncertainty

4% − 4% +

POWHEG+PYTHIA6 POWHEG LO+PYTHIA6 EPOS 3 c > 0.3 GeV/

assoc T

p c < 24 GeV/

D T

p 16 < scale uncertainty

4% − 4% +

baseline-subtraction uncertainty

)

1

D meson pT Soft Hard

(rad) ϕ ∆ 0.5 1 1.5 2 2.5 3 0.2

(rad) ϕ ∆ 0 0.5 1 1.5 2 2.5 3

(rad) ϕ ∆ 0.5 1 1.5 2 2.5 3 (rad) ϕ ∆ 0.5 1 1.5 2 2.5 3

(rad) ϕ Δ 0.5 1 1.5 2 2.5 3 )

1

(rad ϕ Δ d assoc N d D N 1 1 2 3 4 5 6 7 *+ , D + , D Average D = 5.02 TeV s pp, ALICE | < 1 η Δ | < 0.5, | cms D y | c > 0.3 GeV/ assoc T p , c < 8 GeV/ D T p 5 < 4% scale uncertainty ± /ndf = 1.38 2 χ Total fit Near side Away side Baseline

Fit

arXiv:1910.14403v1 [nucl-ex] 31 Oct 2019

POWHEG+PYTHIA6 Ratio of yields to 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 ) c (GeV/

T

p D-meson 5 10 15 20 25 0.4

ALICE

3 3.5 4

Near side

c > 0.3 GeV/

assoc T

p

POWHEG+PYTHIA6 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 ) c (GeV/

T

p D-meson 5 10 15 20 25 0.4

ALICE

3.5 4 4.5

Away side

c > 0.3 GeV/

assoc T

p

) c (GeV/

T

p D-meson

5 10 15 20 25

POWHEG+PYTHIA6 Ratio of baseline to

0.6 0.8 1 1.2 1.4 1.6

Baseline Level

c > 0.3 GeV/ assoc T p ALICE 3

SLIDE 25

K* and φ (ALICE)

Peter Skands

25

Monash U. 2 4 6 8 10 12 14 16 18 20

7 −

10

5 −

10

3 −

10

1 −

10

1

) c ) (GeV/ y d

T

p /(d N

2

d

INEL

N 1/

= 8 TeV, |y| < 0.5 s pp pp INEL PYTHIA 8 Monash 2013 PHOJET EPOS-LHC

ALICE

2 * K + K* 2 4 6 8 10 12 14 16 18 20

) c (GeV/

T

p

1 2 3 Model/Data

2 4 6 8 10 12 14 16 7 −

10

5 −

10

3 −

10

1 −

10

1

) c ) (GeV/ y d

T

p /(d N

2

d

INEL

N 1/

= 8 TeV,|y| < 0.5 s pp pp INEL PYTHIA 8 Monash 2013 PHOJET EPOS-LHC

ALICE

φ

2 4 6 8 10 12 14 16

) c (GeV/

T

p

1 2 3 Model/Data

arXiv:1910.14410v1 [nucl-ex] 31 Oct 2019

3 10 4 10 (GeV) s 0.1 0.2 0.3 0.4 0.5 0.6 /K* φ ) * K + /(K* φ 2 STAR ALICE 3 10 4 10 (GeV) s 0.02 0.04 0.06 π / K* )

π

+ + π /( K* 3 10 4 10 (GeV) s 0.01 0.02 π / φ )

π

+ + π /( φ 2 STAR ALICE 10 2 10 3 10 4 10 (GeV) NN s 0.1 0.2 0.3 0.4 0.5 0.6 /K K* pp d-Au p-Pb Cu-Cu Au-Au Pb-Pb Grand Canonical Thermal Model = 156 MeV ch T STAR ALICE 10 2 10 3 10 4 10 (GeV) NN s 0.05 0.1 0.15 0.2 /K φ pp d-Au p-Pb Cu-Cu Au-Au Pb-Pb Grand Canonical Thermal Model = 156 MeV ch T NA49 STAR PHENIX ALICE

NB: nch dependence measured separately, in arXiv:1910.14397

SLIDE 26

K* and φ multiplicity dependence (ALICE)

Peter Skands

26

Monash U.

5 10 15 20 25 30 35 |<0.5 η | 〉 η /d ch N d 〈 0.6 0.8 1 1.2 1.4 1.6 1.8 2 ) c (GeV/ 〉 T p 〈 ALICE < 0 y 0.5 < − = 5.02 TeV, NN s Pb, − p | < 0.5 y = 7 TeV, | s pp, | < 0.5 y = 13 TeV, | s pp,

K*

5 10 15 20 25 30 35 40 45 |<0.5 η | 〉 η /d ch N d 〈 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 ) c (GeV/ 〉 T p 〈 = 13 TeV s Models: pp PYTHIA6 Perugia 2011 PYTHIA8 Monash 2013 PYTHIA8 Without CR EPOS-LHC DIPSY

φ 5 10 15 20 25 30

|<0.5 η |

〉 η /d

ch

N d 〈 0.6 0.8 1 1.2 1.4 1.6 1.8 ) c (GeV/ 〉

T

p 〈

ALICE = 13 TeV s pp, | < 0.5 y |

+

Ω +

Ω

+

Ξ +

Ξ

φ * K + K* Λ + Λ

S

K

1 10

2

10

3

10

| < 0.5 η |

〉 η /d

ch

N d 〈 0.07 0.1 0.2 0.3 0.4 0.5 1 2 Particle Ratios

2 × φ / Ξ /K K* /K φ

arXiv:1910.14397v1 [nucl-ex] 31 Oct 2019

phi/K ~ constant K*/K decreasing Xi/phi increasing

ALICE Pb 2.76 TeV − Pb Pb 5.02 TeV − p pp 7 TeV pp 13 TeV Models: pp 13 TeV PYTHIA6 Perugia 2011 PYTHIA8 Monash 2013 PYTHIA8 Without CR =156 MeV)

ch

T CSM ( EPOS-LHC DIPSY