1. Hadron Fragmentation New Results from Belle
Matthias Grosse Perdekamp, Illinois
Motivation
Belle and KEK-B
Unpolarized Hadron Fragmentation for
Charged Pions and Kaons
Global Analysis and Comparison with BaBar
Future Measurements of pT Dependence
Transversity 2014
Chia, Domus de Maria, Italy June 9th–13th 2014

2. Motivation: Combined Effort to Measure Transversity Distributions
RIKEN BNL Transversity
Workshop 2000 
Measure CFF and IFF
asymmetries in Belle !
D. Boer, A. Ogawa, MGP
Belle
BaBar
e+e-
~ CFF(z1) x CFF(z2)
~ IFF(z1) x IFF(z2)
~ D(z)
HERMES
COMPASS
JLab
SIDIS
~ δq(x) x CFF(z)
~ δq(x) x IFF(z)
First ideas and attempts at LEP:
A. Efremov, et al.(NPPSuppl. 74, 1999) !
RHIC
pp  jets
~ G(x1)xδq(x2) x CFF(z)
pp  h+ + h- + X
~ G(x1)xδq(x2) x IFF(z)
Transversity, δq(x)
Tensor Charge
Theory
Lattice QCD: Tensor Charge = Σq=u,d∫01δq(x)dx
June 12th

3. Available Results on Spin-Dependent and
Spin-Independent Fragmentation from Belle
Collins FF for charged pions (R. Seidl, Illinois + K. Hasuko RIKEN)
Off-Resonance: Phys.Rev.Lett.96:232002, Transversity 2005
On-Resonance: Phys.Rev.D78:032011, Transversity 2008
(Theoretical aspects: Daniel Boer, Nucl.Phys.B806:23-67,2009)
Interference FF for pion pairs (A. Vossen Illinois/Indiana + R.Seidl, RIKEN)
On-Resonance: Phys.Rev.Lett.107:072004, Transversity 2011
Unpolarized FFs for charged pions and Kaons (M. Leitgab, Illinois)
Collins FF for charged Kaons (F.Giordano, Illinois)
Unpolarized FF : Phys.Rev.Lett. 111:062002,2013
Kaon Collins FF: released at DIS Transversity 2014
Also a first at this year’s Transversity workshop:
STAR results on IFF (A. Vossen, Indiana)
June 12th

4. Motivation for High Statistics Measurement for Hadron Multiplicities at B-Factories
limited data for z>0.7
and at low Q2

5. KEK-B: High Luminosity, L = 2.1 x 1034cm-2s-1 at low Backgrounds
Asymmetric collider: 8 GeV e GeV e+
Ös = GeV , e+e-  ϒ(4S)  BB
Ös = GeV e+e-  qq (u,d,s,c)
Available statistics:
1.8 x 109 events (on resonance) [Collins Analysis]
220 x 106 events (off-resonance) [Spin Averaged D(z)]
(Delphi at LEP ~ 6 x 106 events)
“on”
“off”
Belle detector
KEKB
Critical innovations:
Continuous injection
22 mrad beam crossing
with crab cavities
June 12th

6. KEK-B Critical Innovations: (A) Continuous Injection
(B) 22mrad Beam Crossing with Crab Cavities
(A) Constant Beam Current through
Continuous Injection
(B) Avoidance of parasitic beam
crossings without loss of
luminosity
high energy ring - beam current
22 mrad.
crossing
crab crossing
low energy ring - beam current
∫Ldt vs day time
∫Ldt =1fb-1/day
24 hours
June 12th

7. Belle Detector: Large acceptance, Good Tracking and Particle ID
June 12th

8. Hadron Multiplicity Analysis in Belle
June 12th

9. Belle Results on Hadron Multiplicities for Charged Pions and Kaons
Similar
for Kaons
June 12th

10. Comparison with Previous Data Sets
Pions
Kaons
June 12th

11. Update to DSS Fit Including Belle and BaBar Data
from R. Sassot [Fragmentation Function Workshop in December 2013 in Bloomington]
Overall normalization factors needed to obtain consistent fit with
previous e+e- data sets NBelle=1.058, NBarBar=1.021.
At large z, Belle Multiplicities drop off faster than BarBar’s
June 12th

12. Updated Pion Fragmentation Functions
from R. Sassot [Fragmentation Function Workshop in December 2013 in Bloomington]
Main new feature: gluon FF changes
with inclusion of ALICE data
Belle and BaBar data consistent with
other data sets. Impact limited by
uncertainty in the normalization
June 12th

13. Projections for Super Belle
KEKB Upgrade & Luminosity
Backgrounds & Detectors
Projections for di-hadron yields
and pT dependent yields

14. Upgrade Plan for Super KEKB
Initial target: 10×higher luminosity ~ 21035/cm2/sec
Final goal: L=81035/cm2/sec and ∫L dt = 50 ab-1
Crab cavity
8GeV e-
New IR with crab
crossing and
smaller by*
3.5GeV e+
Assume 5 ab- 1
off-resonance
for FF analysis !
New beam-pipe
with ante-chamber
More RF for higher
beam current
Damping
ring for e+
beam SR

15. New Detector Required for 20 Times Increased Background
(Super -)

16. Super Belle New particle identifier with precise Cherenkov device:
Faster calorimeter with waveform sampling and pure CsI (endcap)
New particle identifier with
precise Cherenkov device:
(i)TOP or fDIRC.
KL/m detection
with scintillator
and next generation
photon sensors
Background tolerant
super small cell
tracking detector
New dead time free
pipelined readout and
high speed
computing systems
Si vertex detector with
high background tolerance
& fast readout

17. Observe pT Dependence of Yields
for e+e- Annihilation into Hadron Pairs
electron
Constrain pT-dependence
of fragmentation functions
h2, z2 pT
Combinations:
z relative hadron
momenta
positron

18. 0.2 < z< 0.25 0.5 < z < 0.55 pT[GeV] pT[GeV]1
10-1
10-2
10-3
10-4
10-5
0.2 < z< 0.25 1
10-1
10-2
10-3
10-4
10-5
0.5 < z < 0.55
Relative Stat. Error
Relative Stat. Error
pT[GeV]
pT[GeV] 1
10-1
10-2
10-3
10-4
10-5 1
10-1
10-2
10-3
10-4
10-5
0.7 < z < 0.75
0.9 < z < 0.95
Relative Stat. Error
Relative Stat. Error
pT[GeV]
pT[GeV]
from Martin Leitgab

19. Summary
High statistics hadron multiplicties for charged pions and kaons available from Belle and BaBar.
Data sets are consistent with existing data from e+e-, pp and SIDIS after changing the normalization by 5.8% for Belle and 2.1% for BaBar.
The difference in normalization is presently not understood and requires further study.
Precise measurements of the pT dependence of FF are possible both with Belle I and Belle II data sets in the future.
June 12th