Top Banner
Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September 5 th - 8 th 2011 1
31

Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Dec 28, 2015

Download

Documents

Lionel Carr
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

1

Measurement of (Interference) Fragmentation Functions in

e+e- at

Anselm Vossen

and Di-Hadron Correlations

and

DiFF Mini WorkshopPavia, Italy, September 5th - 8th 2011

Page 2: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

2

Outline• IFF measurements at Belle

– Observables– Kinematic Distributions– Flavor decomposition (Charm Contributions)– Results– Future Plans

• Phenix– Experiment– Results

• Star– Current status– Future possibilities

Page 3: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

3

Interference FF in Quark Fragmentation

q

qs

k

R

Interference Fragmentation Function:Fragmentation of a transversely polarizedquark q into two spin-less hadron h1, h2 carries anazimuthal dependence:

R

sin

T qk R s

1h

2h

𝑘𝑠𝑞

𝑅𝑅𝑇

𝑧𝑝𝑎𝑖𝑟

= 2 𝐸𝑝𝑎𝑖𝑟 / √ 𝑠𝑚

: quark   momentum:quark   spin  : momentum   difference𝑝h 1−𝑝h 2

transverse   hadron   momentum  difference  ¿𝐸𝑝𝑎𝑖𝑟 /𝐸𝑞

: relative   hadron   pair   momentum: hadron   pair   invariant  mass

Page 4: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

4

o Quark spin direction unknown: measurement of Interference Fragmentation function in one hemisphere is not possible

sin φ modulation will average out.

o Correlation between two hemispheres with sin φRi single spin asymmetries results in cos(φR1+φR2) modulation of the observed di-hadron yield.

Measurement of azimuthal correlations for di-pion pairs around the jet axis in two-jet events!

Spin Dependent FF in e+e- : NeedCorrelation between Hemispheres !

Page 5: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

5

q1

quark-1 spin

Interference effect in e+e-

quark fragmentation will lead to azimuthalasymmetries in di-hadron correlation measurements!

Experimental requirements:

Small asymmetries very large data sample!

Good particle ID to high momenta.

Hermetic detector Observable:cos(φR1+φR2)

modulation measures

Measuring di-Hadron CorrelationsIn e+e- Annihilation into Quarks

electron

positron

q2

quark-2 spin

( )

z1,2 relative pion pair momenta

z2 z1

( )

11H H

φR1φR2

Page 6: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

6

KEKB: L>2.11 x 1034cm-2s-1 !!• Asymmetric collider• 8GeV e- + 3.5GeV e+

• √s = 10.58GeV (U(4S))• e+e-U(4S)BB• Off-resonance production:

10.52 GeV• e+e-qq (u,d,s,c)• Integrated Luminosity: > 1000 fb-1

• >70 fb-1 => continuum

6

Belle detectorKEKB

Page 7: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

7Large acceptance, good tracking and particle identification!

He/C2H6

Page 8: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Interference Fragmentation–thrust methode+e- (+-)jet1()jet2X

transverse spin projection8 21221111 m,zHm,zHA cos

2

2

sin

1 cos

2

1

1hP

2hP

2h1h PP

q

Page 9: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

9

• Similar to previous method• Observe angles j1R+j2R between the event-plane (beam, two-

pion-axis) and the two two-pion planes.

• Theoretical guidance by Boer,Jakob,Radici

jR2

-p jR1

1hP

2hP

3hP

4hP

2h1h PP

4h3h PP

Interference Fragmentation – “ f0 “ method

Page 10: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

10

Cuts and Binning

• Similar to Collins analysis, full off-resonance and on-resonance data(7-55): ~73 fb-1 + 588 fb-1

• Visible energy >7GeV • PID: Purities in for di-pion pairs > 90% • Same Hemisphere cut within pair (p+p-), opposite hemisphere between

pairs• All 4 hadrons in barrel region:-0.6 < cos (q) <0.9• Thrust axis in central area: cosine of thrust axis around beam <0.75• Thrust > 0.8 to remove B-events < 1% B events in sample• zhad1,had2>0.1

• z1 = zhad1+zhad2 and z2 in 9x9 bins

• m 1pp and m 2pp in 8x8 bins: [0.25 - 2.0] GeV

• New: Mixed binning

Page 11: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

11

Kinematics

Page 12: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

12

Opening Cut and Energy Flow

Opening Cut of 0.8 Opening Cut of 0.9

Page 13: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

13

Zero tests: MC

• A small asymmetry seen due to acceptance effect• Mostly appearing at boundary of acceptance• Opening cut in CMS of 0.8 (~37 degrees) reduces

acceptance effect to the sub-per-mille level13

Ph

),cos(ˆ

nPP

nP

h

h

No opening cutOpening cut>0.7Opening cut >0.8

Page 14: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

14

(z1x m1) Binning

arXiv:1104.2425PRL 107, 072004(2011)

Page 15: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

(m1x z1) Binning

arXiv:1104.2425PRL 107, 072004(2011)

15

Page 16: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

16

Subprocess contributions (MC)8x8 m1 m2 binning

tau contribution (only significant at high z)charged B(<5%, mostly at higher mass)Neutral B (<2%)charm( 20-60%, mostly at lower z)uds (main contribution)

Page 17: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Subprocess contributions (MC)

tau contribution (only significant at high z)charged B(<5%, mostly at higher mass)Neutral B (<2%)charm( 20-60%, mostly at lower z)uds (main contribution)

17

9x9 z1 z2 binning

Page 18: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

18

Page 19: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Accessing QCD vacuum fluctuations in Quark Fragmentation

• QCD vacuum is superposition of theta vacua• On microscopic scale this could be accessible in experiments

– First results in STAR – Planned measurements in Belle: – Needed as a ‘tie breaker’– Model Calculations predict 2% effect

• Access to nonperturpative properties of QCD• Transition instantons/sphalerons: Role in Early Universe, baryogenesis …

Page 20: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Anselm Vossen

20

q1

quark-1 spin

Event Topologyelectron

positron

q2

quark-2 spin

z2 z1

z1,2 relative pion momenta

Jet Axis

p+ p-

: Momentum : Spin

• Fragmentation in P-odd bubble leads to left right asymmetry– Difference in ‘Winding number’ gives effective increment in chirality– Spin alignment via chromomagnetic effect– Azimuthal event by event modulation– Measurement: Extract width of distribution of first moments

– Analysis already underway: Is there a Di-hadron Analogue?

1H 1H

Page 21: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Currently underway:• Belle II is a significant upgrade to

Belle and will sample 2 orders of magnitude higher luminosity

• High precision data will enable measurement of– P-odd FFs– Transverse momentum dependent FFs– Charm suppression possible

• IU will develop FEE for Barrel KLM detector crucial for high precision FF measurement of identified particles

Page 22: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Belle Fragmentation activityRIKEN/RBRC Illinois Indiana Titech

Unpol FFse+e-hX:

e+e-(hh)X,(h)(h)X,hhX:

Unpol kT dependence:

Neutral hadrons: (p0 ,h0) John KosterCharged di-hadrons: Ralf Seidl

Charged hadrons (p,K,P):Martin Leitgab

Martin Leitgab

Collins FFse+e-(h)(h)X:

kT dependence:

pp0 : John Kosterpr0: Ralf Seidlpp: Ralf Seidlpp0 : John Koster

pK,KK: Francesca GiordanoFrancesca Giordano

pr±: ?

Interference FF:e+e-(hh)(hh)X

Charged : pp Ralf Seidl

Charged pp: Anselm Vossenpp0 : Anselm Vossen

Charged pK,KK:Nori-aki Kobayashi

Local P :L(polFF,SSA) :Jet-jet asy:

Anselm Vossen

Black: about to startGreen: ongoingGrey: finished

22

Page 23: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

23

Same Hemisphere Correlations?

• Motivation: P-odd FF x Collins (in Single hadron) does not average out

Page 24: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

p+p complementary and increased kinematic reach in x, z

• Kinematic reach of SIDIS data

• Kinematic reach in p+p for single pions at 3<eta<4

• Relative hadron momentum z for p+p (3<eta<4) collisions and SIDIS (COMPASS), only single hadron, di-hadron z1+z2 ‘less different’

z

Mean z: 0.64

PT

Page 25: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

25

Definition of Vectors and Angles

1 2

1 2

1 2

p+p c.m.s. = lab frame

, : momenta of protons

, : momenta of hadrons

( ) / 2

: proton spin orientation

A B

h h

C h h

C h h

B

P P

P P

P P P

R P P

S

))))))))))))))))))))))))))))

))))))))))))))))))))))))))))

))))))))))))))))))))))))))))))))))))))))))

))))))))))))))))))))))))))))))))))))))))))

))))))))))))))

1hP))))))))))))))

2hP))))))))))))))

100 GeVAP))))))))))))))

100 GeVBP))))))))))))))

CP))))))))))))))

BS))))))))))))))

pp hhX

1 2hadron plane: ,

scattering plane: ,

h h

C B

P P

P P

))))))))))))))))))))))))))))

)))))))))))))))))))))))))))) : from scattering plane

to hadron planeR : from polarization vector

to scattering plane S

Bacchetta and Radici, PRD70, 094032 (2004)

2 CR))))))))))))))

Page 26: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

26

PHENIX Detectors used for IFF Analysis

• Use 2 separate spectrometer arms at central rapidity,|h| < 0.35

• Azimuthal coverage: 90° + 90°• Electromagnetic Calorimeters

– PbSC + PbGl– High granularity DhDf=0.010.01

• Tracking of charged particles– Drift chamber, pad chambers

Little p_t dependence of x at mid rapidity, low x

Page 27: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

27

vs Invariant Mass of the PairsinUTA

First measurement of IFF in pp

Results and ProjectionsFrom run 12+13

Page 28: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

Planned Transversity measurements at STAR

• Measurements with current detector– Transversity in Di-Hadron

correlations – p0 in FMS and Encap, p+ /p-

inTPC– Sivers effect in jets in EEMC– Explore jet –jet and gamma –

jet asymmetries

Full azimuth spanned with nearly contiguous electromagnetic calorimetry from -1<h<4

approaching full acceptance detector

Page 29: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

29

R&D for planned STAR forward upgrade

• Forward instrumentation optimized for p+A and transverse spin physics

– Charged Tracking upgrade covering FMS will enable di-hadron measurements and jet measurements

– Star decadal plans calls additionally for PID (e.g. RICH) and pi0/gamma separation (preshower)

FMS

~ 6 GEM disksTracking: 2.5 < η < 4

proton nucleus

• Transverse spin effect dominated by valence quarks accessed in forward direction

Page 30: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

30

Projections forBelle Measurements of IFF in STAR, Channel: (pp0) (pp0)

• Errors one order of magnitude smaller than average asymmetry in (pp)

Hadron pair in second hemisphere:0.77 GeV <Minv< 1.2 GeV

a 12

(580 fb-1 integrated luminosity)

-0.004

0.002

-0.002

0

Page 31: Measurement of (Interference) Fragmentation Functions in e + e - at Anselm Vossen and Di-Hadron Correlations and DiFF Mini Workshop Pavia, Italy, September.

3131

Measuring Light Quark Fragmentation Functions on the ϒ(4S) Resonance

ii

ii

p

npTThrust

ˆ

:

• small B contribution (<1%) in high thrust sample • >75% of X-section continuum under ϒ (4S) resonance• 73 fb-1 662 fb-1

9.44 9.46

e+e- Center-of-Mass Energy (GeV)

0

5

10

15

20

25

(e+

e-

had

ron

s)(n

b)

(1S)10.0010.02

0

5

10

15

20

25

(2S)10.34 10.37

0

5

10

15

20

25

(3S)10.54 10.58 10.62

0

5

10

15

20

25

(4S)9.44 9.46

e+e- Center-of-Mass Energy (GeV)

0

5

10

15

20

25

(e+

e-

had

ron

s)(n

b)

(1S)10.0010.02

0

5

10

15

20

25

(2S)10.34 10.37

0

5

10

15

20

25

5

10

15

20

25

(2S)10.34 10.37

0

5

10

15

20

25

(3S)10.54 10.58 10.62

0

5

10

15

20

(3S)10.54 10.58 10.62

0

5

10

15

20

25

(4S)BB00 BB

e+e-qq̅, q uds∈

e+e-cc̅

0.5 0.8 1.0

4s“off”