Modulations of the di-pion pair x- section at Belle (and the future of FF measurements at BelleII)

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1 Modulations of the di-pion pair x- section at Belle (and the future of FF measurements at BelleII) ANSELM VOSSEN CENTER FOR EXPLORATION OF ENERGY AND MATTER IIFF 2013 December 14 th, 2013

2 Azimuthal angles in the Di-Pion Pair x-section ϕ 2 -π P h2 P h1 R P h + P 1 h2 π-ϕ 1 e + e - è (π + π - ) jet1 (π + π - ) jet2 X Find pion pairs in opposite hemispheres Observe angles ϕ 1, ϕ 2 between the event-plane (beam, jet-axis) and the two two-pion planes. 2

3 Di-hadron Cross Section from Boer,Jakob,Radici[PRD 67,(2003)] Expansion of Fragmentation Matrix Δ: encoding possible correlations in fragmentation à See talk by Piet Mulders (k: P h1 +P h2 ) Measure Cos(φ R1 + φ R2 ), Cos(2(φ R1 -φ R2 )) Modulations!

4 Di-hadron Cross Section from Boer,Jakob,Radici[PRD 67,(2003)] Δ: Fragmentation Matrix, encoding possible correlations in fragmentation k: P h1 +P h2 Spin independent part from Boer,Jakob,Radici[PRD 67,(2003)]

5 Di-hadron Cross Section from Boer,Jakob,Radici[PRD 67,(2003)] Δ: Fragmentation Matrix, encoding possible correlations in fragmentation Helicity dependent correlation of Intrinsic transverse momentum with k: P h1 +P h2 Di-hadron plane

6 Cross Section Δ: Fragmentation Matrix, encoding possible correlations in fragmentation Correlation of transverse spin with Di-hadron plane Measure Cos(φ R1 + φ R2 ), Cos(2(φ R1 -φ R2 )) Modulations!

7 Measure Cos(φ R1 + φ R2 ), Cos(2(φ R1 -φ R2 )) modulations to access H <,G 1 In addition: D. Boer at the Miniworkshop on Dihadron Fragmentation Functins, Pavia, 2011: Cos(φ R1 + φ R2 ) is related to jet-handedness correlations Signal would hint at P-violation, expected to vanish in factorized approach So far Belle has measured Cos(φ R1 + φ R2 ) correlation (see Ralf s talk)

8 D. Boer, Pavia 2011 DiFF workshop

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10 Measurement at Belle See talks by Francesca and Ralf Follow IFF analysis: Full off/on resonance dataset Visible energy > 7 GeV Opposite hemisphere between pion pairs Thrust Axis in central area cos(thrust θ CMS ) < 0.5 All hadron in barrel region: Thrust θ - Hadron θ <0.55 rad Thrust > 0.8 : remove B-events (<1% left) Z had1 >0.2 Do 2D fit for all three modulations φ R2 φ R1

11 Study of Asymmetries in Belle MC Belle uses Pythia+Evtgen (implements decay tables) After detector asymmetries of the order of 1% (0.5%) are left. Pythia w/o detector is consistent with this Possible culprits: gluon radiation, weak decays, detector effects (but cannot be all) à Use jets with min energy, do not allow more then 10% of missing energy Use all di-pion pairs (identified with purity >95%)

12 New: Use Jet Reconstruction at Belle We use anti-kt algorithm implemented in fastjet Cone radius R=0.55 Min energy per jet 2.75 Only allow events with 2 jets passing energy cut (dijet events) Only particles that form the jet are used in the asymmetry calculation Missing energy cut of 1 (handedness) /1.5(G1T) GeV (~10%/15%) Thrust cut of 0.8< T< 0.95

13 Jet Kinematics <N>=3.6

14 Missing Energy cut to remove possible contributions from weak decays uds charm Indicated the cuts at 1GeV and 1.5 GeV in missing CMS energy. Effect on uds is 32/14%, charm is cut by48/24% respectively

15 Asymmetries for phi1-phir with the different cuts No cut Cut of 1.5 GeV Notice that ONLY the last m_inv bin is a problem and that the asymmetry is only around 1% Cut of 1.0 GeV

16 Mixed event subtraction Phi-Phi2 exhibits some acceptance effects à subtract mixed events sorted by jet topology

17 Mixed event subtracted flattens acceptance related false asymmetries Remaining asymmetries in MC+their stat error used to estimate systematics

18 Asymmetries in Data persists for Cos(φ R1 -φ R2 ) Work in progress Work in progress

19 Asymmetries for Cos(2(φ R1 -φ R2 )) (G 1 ) small Work in progress Work in progress

20 Asymmetries for Cos(2(φ R1 -φ R2 )) (G 1 ) small Work in progress

21 Asymmetries for Cos(2(φ R1 -φ R2 )) (G 1 ) small Work in progress

22 Summary and Outlook Belle is measuring Cos(φ R1 -φ R2 ) di-hadron correlations for identified pion pairs in jets Difference of angles leads to more severe detector effects We only see small signal for G 1 Correlation effects that are present in Pythia for Cos(φ R1 -φ R2 ) modulation have to be better understood Are they real? Can we rely on the MC? à More tests needed Hermeticity requirements and jet reconstruction removes most false asymmetries Optimization of jet R still needed Lower jete cut and use highest pair? Cos(2(φ R1 -φ R2 )) at 1% level remains at high M inv, z Is this QCD? Weak decays? Outlook: Belle II

23 KEKB/Belleà SuperKEKB, Upgrade Aim: super-high luminosity ~10 36 cm -2 s -1 (~40x KEK/Belle) Upgrades of Accelerator (Microbeams + Higher Currents) and Detector (Vtx,PID, higher rates, modern DAQ) Significant US contribution to PID/electronics 23 First beam in the machine, end of

24 24

25 Crucial for Successful Jlab 12 GeV program -more statistics (x40 Good PID, enabling channels with more than one kaon (efficiency >95%, (Belle ~90%), Fake rate < 5% (Belle 10-15%) Good Vtx detection: charm isolation à Successful FF program at Belle II a must!

26 BACKUP

27 Measurement of Fragmenta/on KEKB: L>2.11 x 1034cm-2s-1 Asymmetric collider: + 8GeV e GeV e s=10.58 GeV (!(4S)) + e e!!(4s)!bb -1 Integrated Luminosity: > 1000 fb Continuum production: GeV + e e!(u, d, s, c) -1 => continuum >70 fb Anselm Vossen 27 Belle detector KEKB 27

28 Measuring Light Quark Fragmentation Functions on the ϒ(4S) Resonance e + e - à qq, q uds e + e - à cc 28 σ(e + e - hadrons)(nb) off 4s B + B B 0 B 0 5 ϒ(1S) ϒ(2S) ϒ(3S) ϒ(4S) e + e - Center-of-Mass Energy (GeV) Thrust : T = i i p i p nˆ i small B contribu3on (<1%) in high thrust sample >75% of X- sec3on con3nuum under ϒ (4S) resonance ~100 H - 1 è ~1000 H - 1

29 Belle II Detector at SuperKEKB (L x 40) and IU contributions to Barrel Particle ID Barrel PID instrumental for fragmentation function measurements EM Calorimeter: CsI(Tl), waveform sampling (barrel) Pure CsI + waveform sampling (end-caps) K L and muon detector: Resistive Plate Counter (barrel outer layers) Scintillator + WLSF + MPPC (end-caps, inner 2 barrel layers) RPC Front End Electronics, Concentrator boards for barrel and endcap scintillator layers Particle Identification Time-of-Propagation counter (barrel) Active HV Divider board for MCP-PMT Validation of FPGA code of itop e- (7GeV) Vertex Detector 2 layers DEPFET + 4 layers DSSD Vertex resolution improved by order of magnitude: Separate charm/uds e+ (4GeV) RPC test stand at IU to test electronics: E. Zarndt, S. Arnold

30 Handedness Correlations π + Thrust direction π + L R π - Handedness: ( k + k ) t / k + k =sinφ?@>@ 0 L/R Jet handedness: N R N L / N R + N L π - C: N RL + N LR N RR N LL / N RL + N LR + N RR + N LL 30

31 QCD Vacuum Transitions carry Chirality QN 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 Similar mechanism to EW baryogenesis

32 Kharzeev, McLerran and Warringa, arxiv: , Fukushima, Kharzeev and Warringa, arxiv: QCD Vacuum Transitions carry Chirality QN arxiv: v2 [

33 Handedness Correlations π + Thrust direction π + L R Q=1 π - Handedness: ( k + k ) t / k + k =sinφ?@>@ 0 L/R Jet handedness: N R N L / N R + N L π - C: N RL + N LR N RR N LL / N RL + N LR + N RR + N LL Expect negative correlation for local p-odd effect 33

34 Quark Spinà Azimuthal Dependence s q q R r h 1 h 2 φ RS R r k s q R R T z pair =2 E pair / s m & :quark momentum :quark spin : momentum difference p h1 p h2 transverse hadron momentum difference = E pair / E q :relative hadron pair momentum :hadron pair invariant mass 34 Interference Fragmentation Function: Fragmentation of a transversely polarized quark q into two spin-less hadron h1, h2 carries an azimuthal dependence: ( k R T ) s q sin RS

35 Measurement at Belle leads to first point by point extraction of Transversity A 12 Cos(φR1-φR2) H < 1 H < 1 + A UT h 1 H < 1 M. Radici at FF workshop, RIKEN, 11/2012 See also: Courtoy: Phys. Rev. Lett. 107:012001,2011 More Data from future experiments Jlab, RHIC, CERN