[PPT] - Nonperturbative Transverse Momentum Effects in Dihadron and Direct PowerPoint Presentation

SLIDE 1

Nonperturbative Transverse Momentum Effects in Dihadron and Direct Photon-Hadron Angular Correlations

Joe Osborn for the PHENIX Collaboration

University of Michigan

QCD-N’16, July 12, 2016

Joe Osborn (UM) QCD-N 2016 12/07/16 1 / 21

SLIDE 2

Universality and Factorization in TMDs

Drell-Yan SIDIS Sign change in Sivers TMD PDF predicted due to initial-state vs. final-state gluon exchange with proton remnants between DY and SIDIS: modified universality! What about p+p → h1h2 where both initial- and final-state interactions are possible?

Joe Osborn (UM) QCD-N 2016 12/07/16 2 / 21

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TMD Factorization Breaking

Rogers and Mulders paper predicts QCD factorization breaking in dihadron production from p+p collisions in a TMD framework (Phys. Rev. D 81,094006 (2010)) Back-to-back two particle angular correlations give sensitivity to initial- and final-state transverse momentum kT and jT ≥2 gluons exchanged with proton remnants leads to predicted breakdown

Joe Osborn (UM) QCD-N 2016 12/07/16 3 / 21

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Direct Photons and Dihadrons

Direct photon-hadron and dihadron correlations both predicted to be sensitive to factorization breaking effects in PHENIX Assuming factorization, direct photon-hadrons probe three nonperturbative functions, while dihadrons probe four Direct photons offer one less avenue for gluon exchange in the final-state: fewer/different effects?

Joe Osborn (UM) QCD-N 2016 12/07/16 4 / 21

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Angular Correlation Observables

Direct photon-hadron production Dihadron production pout = passoc

T

sin ∆φ

Joe Osborn (UM) QCD-N 2016 12/07/16 5 / 21

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PHENIX Detector

PHENIX central arms

∆φ ∼ π |η| <0.35

Electromagnetic Calorimeter (PbSc/PbGl) provides isolated direct photon and π0 → γγ detection Drift Chamber (DC) and Pad Chambers (PC) provide nonidentified charged hadron detection New results from 2012/2013 √s=510 GeV p+p runs

Joe Osborn (UM) QCD-N 2016 12/07/16 6 / 21

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∆φ Correlations for π0-h± and Direct γ-h±

1

1 2 3 4 0.5

<2 GeV/c

assoc T

1<p ⊗ <15

trig T

12<p

1

1 2 3 4 0.2

<4 GeV/c

assoc T

3<p ⊗ <15

trig T

12<p

1

1 2 3 4 0.1

<10 GeV/c

assoc T

5<p ⊗ <15

trig T

12<p

1

1 2 3 4 0.5

<2 GeV/c

assoc T

1<p ⊗ <12

trig T

9<p

1

1 2 3 4 0.2

<4 GeV/c

assoc T

3<p ⊗ <12

trig T

9<p

1

1 2 3 4 0.1

<10 GeV/c

assoc T

5<p ⊗ <12

trig T

9<p

1

1 2 3 4 0.5

<2 GeV/c

assoc T

1<p ⊗ <9

trig T

8<p

1

1 2 3 4 0.2

<4 GeV/c

assoc T

3<p ⊗ <9

trig T

8<p =510 GeV s p+p at |<0.35 η |

1

1 2 3 4 0.1

<10 GeV/c

assoc T

5<p ⊗ <9

trig T

8<p

±

h

γ Isolated Direct

±

h

π Underlying Event

[rad] φ ∆

1

[rad] φ ∆ d dN

trig

N 1

PH ENIX

preliminary

Two jet structure visible for π0-h±, isolation cut on near side for direct γ-h± Direct γ-h± probes smaller jet energy due to emerging from hard scattering at LO

Joe Osborn (UM) QCD-N 2016 12/07/16 7 / 21

SLIDE 8

p2
ut Extracted from Fits to ∆φ Correlations

[GeV/c]

trig T

p

4 5 6 7 8 9 10 11 12 13 14

[GeV/c] 〉

2

ut

p 〈

1 2 3 4 5 |<0.35 η | =510 GeV s p+p at

<2 GeV/c

assoc T

1<p <3 GeV/c

assoc T

2<p <4 GeV/c

assoc T

3<p

±

h

π

PH ENIX

preliminary [GeV/c]

trig T

p

4 5 6 7 8 9 10 11 12 13 14

[GeV/c] 〉

2

ut

p 〈

1 2 3 4 5 |<0.35 η | =510 GeV s p+p at

<2 GeV/c

assoc T

1<p <3 GeV/c

assoc T

2<p <4 GeV/c

assoc T

3<p

±

h

γ Isolated Direct

PH ENIX

preliminary

p2
ut characterizes away-side jet width and decreases with hard

scale ptrig

T

Sensitive to perturbative and nonperturbative kT and jT

Joe Osborn (UM) QCD-N 2016 12/07/16 8 / 21

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pout Distributions

pout shows two distinct regions: gaussian and power law Gaussian fits clearly fail past ∼1.3 GeV/c Indicates transition from nonperturbative to perturbative kT and jT

[GeV/c]

ut

p

8
6
4
2

2 4 6 8

1

[GeV/c]

ut

dp dN

trig

N 1

11

10

10

10

9

10

8

10

7

10

6

10

5

10

4

10

3

10

2

10

1

10 1 10

2

10

=510 GeV s p+p at |<0.35 η | 3 π 4 < φ ∆ < 3 π 2 <10 GeV/c

assoc T

0.7<p

Gaussian Fit Range: [-1.1,1.1] GeV/c

±

h

π <5 GeV/c

trig T

4<p )

1

<6 GeV/c (x10

trig T

5<p )

2

<7 GeV/c (x10

trig T

6<p )

3

<8 GeV/c (x10

trig T

7<p )

4

<9 GeV/c (x10

trig T

8<p )

5

<12 GeV/c (x10

trig T

9<p )

6

<15 GeV/c (x10

trig T

12<p

±

h

γ

PH ENIX

preliminary

Note: Curves are Kaplan and Gaussian fits, not calculations!!

Joe Osborn (UM) QCD-N 2016 12/07/16 9 / 21

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Gaussian Widths of pout

[GeV/c]

trig T

p

4 5 6 7 8 9 10 11 12 13 14

Gaussian Width [GeV/c]

0.5 0.6 0.7 0.8

Linear Fit π Linear Fit γ Isolated Direct <10 GeV/c

assoc T

0.7<p Fit Range: [-1.1,1.1] GeV/c |<0.35 η | =510 GeV s p+p at γ PHENIX Isolated Direct π PHENIX γ PYTHIA Perugia0 Isolated Direct π PYTHIA Perugia0 PH ENIX preliminary

Gaussian widths of pout distributions decrease with hard scale ptrig

T

Sensitive to only nonperturbative kT and jT in the nearly back-to-back region ∆φ ∼ π PYTHIA replicates slope almost exactly, but shows 15% difference in magnitude of widths

Joe Osborn (UM) QCD-N 2016 12/07/16 10 / 21

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Expectations from Collins-Soper-Sterman (CSS) Evolution

Expectation from CSS evolution is that any momentum width sensitive to nonperturbative kT grows with the hard scale

Broadening due to increased phase space for hard gluon radiation

Note that the CSS evolution equation comes directly out of the derivation for TMD factorization

]

2

[GeV/c

µ µ

M

20 30 40 50 60 70 80 90 100

Gaussian Width [GeV/c]

2 3 4 5 PYTHIA Perugia0 Simulation Drell-Yan Dilepton >4 GeV/c

lep T

p |<0.35 η | =510 GeV s p+p at

PYTHIA confirms expectation from CSS evolution for same

bservable

Joe Osborn (UM) QCD-N 2016 12/07/16 11 / 21

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SIDIS and DY/Z Measurements

DY/Z and SIDIS, where factorization is predicted to hold, have been shown to follow CSS evolution Phenomenological studies in both interactions show increasing momentum widths when sensitive to small kT scale

Phys. Lett. B 633, 710 (2006)

(DY/Z)

Phys. Rev. D 89, 094002 (2014) (SIDIS)

Joe Osborn (UM) QCD-N 2016 12/07/16 12 / 21

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Conclusions

Factorization breaking has been predicted in p+p → h + X collisions for observables sensitive to nonperturbative transverse momentum New measurements from PHENIX of nearly back-to-back dihadron and isolated direct photon-hadron correlations at √s=510 GeV Angular correlations sensitive to initial-state kT and final-state jT show decreasing momentum widths with hard scale in p + p → h + X Literature shows that Drell-Yan/Z and SIDIS interactions, which CSS evolution describes, exhibit increasing momentum widths with hard scale Paper draft undergoing internal review process!

Joe Osborn (UM) QCD-N 2016 12/07/16 13 / 21

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Back Up

Joe Osborn (UM) QCD-N 2016 12/07/16 14 / 21

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Analysis Methods

Correlated π0 − h± or isolated γ − h± are collected and corrected with:

Charged hadron efficiency Acceptance correction

Direct photons undergo additional statistical subtraction to remove decay photon background, estimated with Monte Carlo probability functions Isolation and tagging cuts remove decay photon background and NLO fragmentation photons

Probability for a π0 to decay to a photon which could not be tagged with 5 < pT < 7 GeV/c in PHENIX Y iso

dir =

1 Riso

γ − 1

Riso

γ Y iso inc − Y iso dec

Joe Osborn (UM)

QCD-N 2016 12/07/16 15 / 21

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Riso

γ

Measurement at √s=510 GeV

Riso

γ

measured for statistical subtraction of isolated decay photon contribution Rγ measured in PHENIX and corrected by tagging and isolation efficiencies Riso

γ

>1 indicates isolated direct photon production

[GeV/c]

γ T

p

7 8 9 10 11 12 13 14

iso γ

R

1 1.2 1.4 1.6 1.8 2 2.2

=510 GeV s p+p at |<0.35 η |

PH ENIX

preliminary

Riso

γ

= Rγ (1 − ǫtag

dec)(1 − ǫniso dec )

Niso

inc

Ninc

Joe Osborn (UM) QCD-N 2016 12/07/16 16 / 21

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PYTHIA pout Distributions

PYTHIA π0-h± and isolated γ-h± correlations analyzed similarly to data PYTHIA exhibits similar characteristics to data: nonperturbative transitioning to perturbative region Initial and final state interactions possible in PYTHIA: all particles are forced to color neutralize

[GeV/c]

ut

p

5
4
3
2
1

1 2 3 4 5

1

[GeV/c]

ut

dp dN

trig

N 1

9

10

8

10

7

10

6

10

5

10

4

10

3

10

2

10

1

10 1 10

2

10

3

10

±

h

π <5 GeV/c

trig T

4<p )

1

<6 GeV/c (x10

trig T

5<p )

2

<7 GeV/c (x10

trig T

6<p )

3

<8 GeV/c (x10

trig T

7<p )

4

<9 GeV/c (x10

trig T

8<p )

5

<12 GeV/c (x10

trig T

9<p )

6

<15 GeV/c (x10

trig T

12<p

PYTHIA Perugia0 Simulation =510 GeV s p+p at <10 GeV/c

assoc T

0.7<p 3 π 4 < φ ∆ < 3 π 2 |<0.35 η |

±

h

γ

Joe Osborn (UM) QCD-N 2016 12/07/16 17 / 21

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Other DY/Z and SIDIS Refs.

Phys. Rev. D 67, 073016 (2003)

(DY/Z)

Phys. Rev. D 61, 014003 (2000)

(SIDIS)

Joe Osborn (UM) QCD-N 2016 12/07/16 18 / 21

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√s=200 GeV Results

Previous PHENIX result at √s=200 GeV with larger errors (Phys. Rev. D 82, 072001 (2010)) Next step: analyze recent Run 15 √s=200 GeV p+p and p+A data from RHIC! 6x luminosity in Run 15 p+p, as well as first result from p+A 2 < passoc

T

< 5

Joe Osborn (UM) QCD-N 2016 12/07/16 19 / 21

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Other Measurements in Literature

Other RHIC publications show the same effect in

p2
ut and

away-side width All previous analyses motivated by different physics goals: fragmentation functions, partonic energy loss in QGP, etc. PRD 82, 072001 (2010) (PHENIX) PRD 74, 072002 (2006) (PHENIX)

[GeV/c]

assoc T

p 2 4 6 8 10 12 14 16 Awayside Gaussian Width [rad] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 <15 GeV/c

jet,rec T

10<p <40 GeV/c

jet,rec T

20<p =200 GeV s STAR p+p at

Phys. Rev. Lett. 112,122301

Correlations

±

Jet-h

PRL 112,122301 (2014) (STAR)

Joe Osborn (UM) QCD-N 2016 12/07/16 20 / 21

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Possible Links to Color Coherence Effects?

D0, CDF, CMS have all published papers on evidence for ”color coherence effects” Color flow and ”antenna” traced through hard scatter with gluon radiation Few citations though, relatively unknown work! CMS: Eur.Phys.J. C74 (2014) no.6, 2901 CDF: Phys. Rev. D 50, 5562 (1994) D0: Phys. Lett. B 414, 419 (1997)

Joe Osborn (UM) QCD-N 2016 12/07/16 21 / 21