Prospects for Detecting Local Parity Violating Effects in Quark Fragmentation at. and

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1 Prospects for Detecting Local Parity Violating Effects in Quark Fragmentation at and S Hadrons Quark Anselm Vossen 1

2 CP-Violation in quark Fragmentation 2

3 Transitions in the QCD vacuum carry net chirality The QCD Vacuum Difference in winding number: Net chirality carried by Instanton/Sphaleron Vacuum states are characterized by winding number Transition amplitudes: Gluon configurations, carry net chirality e.g. quarks: net spin momentum alignment Picture: H. Warringa, 3

4 Event Topology in e+ e- electron 4

5 Event Topology in e+ e- electron positron 5

6 Event Topology in e+ e- electron quark-2 spin q positron q 1 quark-1 spin Jet Axis Transverse polarization: sin 2 q/(1+cos 2 q) 6

7 Event Topology in e+ e- electron q 2 z 1,2 relative pion momenta quark-2 spin q q 11 positron quark-1 spin z 1 Jet Axis Transverse polarization: sin 2 q/(1+cos 2 q) 7

8 Event Topology in e+ e- electron q 11 z 2 z 1 q 2 z 1,2 relative pion momenta quark-2 spin q positron quark-1 spin Jet Axis Transverse polarization: sin 2 q/(1+cos 2 q) 8

9 Event Topology in e+ e- electron q 1 z 2 z 1 q 2 z 1,2 relative pion momenta quark-2 spin positron quark-1 spin Jet Axis Transverse polarization: sin 2 q/(1+cos 2 q) 9

10 Jet Handedness Sensitive to quark Chiralities Chirality Chirality Handedness: k + k t k + k? = sinφ >0 L/R Jet handedness: N R N L N R + N L Efremov, Khazeev, Phys. Lett. B366,

11 Fragmentation in the Big Bubble Efremov, Khazeev, Phys. Lett. B366,

12 Jet Handedness Sensitive to quark Chiralities Thrust direction L R Handedness: k + k t k + k? = sinφ>0 L/R Jet handedness: N R N L N R + N L C: N RL + N LR N RR N LL N RL + N LR + N RR + N LL Expect positive correlation for P-odd effect (A.E., D.K: 0.5%, Delphi Prelim: ~3%, naively very high instanton rate (every second quark?)) 12

13 Measurement of Fragmentation (till June 30 th 2010) KEKB: L>2.11 x cm -2 s -1 Asymmetric collider: 8GeV e GeV e + s=10.58 GeV ( (4S)) e + e - (4S) BB Integrated Luminosity: > 1000 fb -1 Continuum production: GeV e + e - (u, d, s, c) >70 fb -1 => continuum KEKB Belle detector Anselm Vossen

14 He/C2H6 Large acceptance, good tracking and particle identification! Collins Asymmetries in Belle

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16 KEKB/Belle upgrade ( ) Aim: super-high luminosity ~10 36 cm -2 s -1 Upgrades of Accelerator (Microbeams + Higher Currents) and Detector (Vtx,PID, higher rates, modern DAQ) Significant US contribution 16

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18 Belle: Vast improvement in Fragmentation Function Precision Pion and Kaon Yields Lower CME: Advantage: longer formation time of mesons (larger effects of Chromo B field on quark) Disadvantage: Lower Multiplicities 18

19 Spin Projection in Barrel and Endcap 1-sin 2 q/(1+cos 2 q) q sin 2 q/(1+cos 2 q) q 19

20 First Look at Handedness Correlation Zero test Should be zero. Effect probably due to insufficient separation of hemispheres Work in Progress. 20

21 Chiral Magnetic Effect leads to Charge Separation Kharzeev, McLerran and Warringa, arxiv: , Fukushima, Kharzeev and Warringa, arxiv:

22 Chiral Magnetic Effect leads to Charge Separation arxiv: v2 [ In Heavy Ion Collisions charged particle correlations agree with expectations from p-odd bubbles But: can also be explained by other dynamical effects in the quark gluon plasma B approx G 22

23 Event Topology in e+ e- electron q 1 z 2 z 1 q 2 quark-2 spin quark-1 spin Jet Axis z 1,2 relative pion momenta positron 23

24 Event Topology in e+ e- electron q 1 z 2 z 1 q 2 quark-2 spin quark-1 spin Jet Axis z 1,2 relative pion momenta positron 24

25 Fragmentation in P odd Bubbles leads to Azimuthal Asymmetries : Momentum : Spin Fragmentation in P-odd bubble leads spin-momentum correlation Difference in Winding number gives effective increment in chirality Spin alignment via chromomagnetic-electric effect Azimuthal event by event modulation Measurement: Extract width of distribution of first moments 25

26 Mix of P-odd FF with Collins FF leads to Event by Event Asymmetries Collins Effect Left Right (Angular Momentum Conservation) Up-Down : Momentum : Spin Kang, Kharzeev: Phys.Rev.Lett.106:042001,2011: Coupling to Collins FF leads to sin(f 1 f 2 ) asymmetry Compare to Collins x Collins ~ (P-odd FF) x (P-odd FF): cos(f 1 f 2 ) Averages out Event by Event since we do not know if quark or antiquark is in p-odd bubble What about flavors or spin 1? r + x compared with x Collins is sensitive to spin 26 Expect sign change for Collins but not for P-Odd FF (sensitive to quark flavor)

27 Transverse Spin Dependent FF measurements Di-hadron Advantage: No contribution by Gluon radiation ( ) electron q 1 ( ) f 1 f 2 z 1,2 relative pion pair momenta z 2 q 2 z 1 quark-2 quark-1 spin positron spin A.V. et. al, PRL 107, (2011) 27

28 First try. Use unbinned maximum likelihood fit for each event - >extract asymmetry A Width of distribution of A is indication of effect Compare with simulation Physical effect has to have linear dependence on giving the transverse spin projection sin 2 q e - q q e + 1 cos 2 q q Ratio of widths Data/MC A 2 sin q 2 1 cos q 28

29 Development of a more robust Correlator Naively: [N + UpN - Down-N + UpN + Down + ( ) ]/ Or Cos(f f ) S P 29

30 Can compare with Collins Naively: [N + LeftN - Right-N + LeftN + Right+ ( ) ]/ Or Sin(f f ) P S 30

31 However: Multiplicity Small, same effect from momentum conservation Subtract Sin(f f ) (independent of event plane)? S P 31

32 Summary & Outlook Probing local parity violating effects in quark fragmentation independent probe Belle & Belle II allow high precision measurement Low Multiplicity per event is challenging Need simple correlators Jet Handedness seems appropriate: Signal magnitude? Transverse Spin effects advantageous for Belle acceptance (~factor 2 higher signal) Use Vector Mesons? 32

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34 Significance Access to QCD vacuum structure First observation of Sphaleron/Instanton induced processes: non-perturbative topological objects In EW sector similar transitions are needed for Baryogenesis Need independent probe! 34

35 Accessing QCD vacuum fluctuations in Quark Fragmentation Transitions between QCD vacuum ground states by non-perturbative gluon configurations: On microscopic scale quarks coupling to these leads to P-odd effects First results at STAR and PHENIX Planned measurements in Belle: needed as a tie breaker Model Calculations predict 2% effect Access to nonperturpative properties of QCD Simulation by Adelaide 35

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38 Fragmentation in the Big Bubble Efremov, Khazeev, Phys. Lett. B366,

39 39

40 Handedness Thrust direction L R Handedness: k + k t k + k? = sinφ>0 L/R Jet handedness: N R N L N R + N L C: N RL + N LR N RR N LL N RL + N LR + N RR + N LL Expect positive correlation for p-odd effect 40

41 Measurements of Fragmentation Functions in e+e- at Belle KEK-B: asymmetric e + (3.5 GeV) e - (8 GeV) collider: - s = GeV, e + e - U(4S) B B - s = GeV, e+e- qqbar (u,d,s,c) continuum ideal detector for high precision measurements: - tracking acceptance θ [17 ;150 ]: Azimuthally symmetric - particle identification (PID): de/dx, Cherenkov, ToF, EMcal, MuID Available data: ~1.8 *10 9 events at GeV, ~220 *10 6 events at GeV KEKB Belle detector 41/18

42 Measuring transverse spin dependent di-hadron Correlations In unpolarized e + e - Annihilation into Quarks j 2 ( ) electron q 1 z 2 q 2 z 1 quark-2 spin quark-1 spin z 1,2 relative pion pair momenta positron ( ) j 1 Interference effect in e + e - quark fragmentation will lead to azimuthal asymmetries in di-hadron correlation measurements! Experimental requirements: Small asymmetries very large data sample! Good particle ID to high momenta. Hermetic detector 42

43 Results or IFF at (z 1 x m 1 ) Binning 43 AV et. al, PRL 107, (2011)

44 Spin-Averaged FF from Pion and Kaon Multiplicities In LO: FF D i h describes probability for a parton i to fragment into a hadron h e - γ* q Extraction from Experimental Data e + q h D q h FF at different energy scales relatable by DGLAP evolution equations FFs D i h can be extracted from e+e- data in pqcd analysis: N h ( z, Q measured: hadron multiplicity 2 ) pqcd fit 1 tot had NLO QCD d e C i q, q, g e hx ) dz NLO i ( z, ) D s h i z ( z, Q 2 E ) cms h s 2 extracted: FFs 44

45 Extraction from Experimental Data recent extractions of unpolarized FFs D h i propagating experimental uncertainties: First FF extraction including uncertainties (e + e - ): Hirai, Kumano, Nagai, Sudoh (KEK) Phys. Rev. D 75, (2007) 'Global' Analyses (e + e -, SIDIS, pp): de Florian, Sassot, Stratmann Phys. Rev. D 75, (2007) and Phys. Rev. D 76, (2007) large uncertainties (esp. gluon FF) due to: D π+ i - Lack of precise data at low energy scales (far from LEP) - Lack of precise data at high z Improve knowledge of FF via high precision hadron measurement at low Q 2 45

46 Systematic Corrections-Particle Misidentification/PID Calibration Particle misidentification expected to be largest uncertainty: particle identification probabilities p( i -> j ): probability that particle of species i PID-selected as particle of species j. Physical particle π Belle PID likelihood information from: Drift Chamber (de/dx), Cherenkov, ToF, Calorimeter, Muon Detector p( π -> e ) p( π -> µ ) p( π -> π ) p( π -> K ) p( π -> p ) Reconstructed particle e µ π K p p( e -> e) p( µ -> e) p( π -> e ) p( K -> e ) p( p -> e ) [P]ij = p( e -> µ) p( µ -> µ) p( π -> µ ) p( e -> π) p( µ -> π) p( π -> π ) p( K -> µ ) p( K -> π ) p( p -> µ ) p( p -> π ) N x N N N N N e K p ~ ^ Nj = P Ni p( e -> K) p( e -> p) p( µ -> K) p( µ -> p) p( π -> K ) p( π -> p ) p( K -> K ) p( K -> p ) ^ ~ Ni = P -1 Nj : p( p -> K ) p( p -> p ) correction through inversion of matrix. 46

47 Pion and Kaon Multiplicities Preliminary Results Binning in z: width = 0.01; yields normalized to hadronic cross section Systematic uncertainties: z ~0.6: 1% (2%) for π (K); z ~0.9: 14% (50%) for π (K) π - Additional normalization uncertainty of 1.4% not shown. Belle experimental data, ~220M events K - 47

48 Summary and Outlook RHIC collected data in polarized p+p from s=62.4 GeV s=500 GeV Non-zero signals for correlation measurements in the central region single TSA in forward region Data taken this year will be able to probe p t dependence of A N, access transversity in dihadron and Collins asymmetries Belle measured unpolarized yield of pion and Kaons Transverse spin dependent single and di-hadron FFs 48

49 Current Analysis (not public yet) Use unbinned maximum likelihood fit for each event - >extract asymmetry A Width of distribution of A is indication of effect Compare with simulation Physical effect has to have linear dependence on giving the transverse spin projection sin 2 q e - q q e + 1 cos 2 q q Ratio of widths Data/MC A 2 sin q 2 1 cos q 49

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51 Pion and Kaon Multiplicities Preliminary Results Binning in z: width = 0.01; yields normalized to hadronic cross section Systematic uncertainties: z ~0.6: 1% (2%) for π (K); z ~0.9: 14% (50%) for π (K) π - Additional normalization uncertainty of 1.4% not shown. Belle experimental data, ~220M events K - 51