Kai Yi, BaBar/SLAC 1 e + e - Annihilation into Quasi-two-body Final States at 10.58 GeV --Expected or unexpected? • Introduction • Analyses of exclusive processes: --e + e - ,(C=+1) TVPA --e + e - + - (C=1 ? ) 1 *+TVPA FSI? --e + e - (C=1 ) s dependence --e + e - pp pp fragmentation (very preliminary) • Summary • Outlook Kai Yi, SLAC
44
Embed
Kai Yi, BaBar/SLAC1 e + e - Annihilation into Quasi-two-body Final States at 10.58 GeV --Expected or unexpected? Introduction Analyses of exclusive processes:
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
Kai Yi, BaBar/SLAC 1
e+e- Annihilation into Quasi-two-body Final States
at 10.58 GeV --Expected or unexpected?
• Introduction• Analyses of exclusive processes: --e+e-, (C=+1) TVPA --e+e-+- (C=1 ? ) 1 *+TVPA FSI? --e+e- (C=1 ) s dependence --e+e-pp pp fragmentation (very preliminary)• Summary • Outlook
Kai Yi, SLAC
Kai Yi, BaBar/SLAC 2
Introduction—General Information
(e+e-hadrons) ~ 3 nb @10.6 GeV
• The design goal of the B factory is the study of B physics.
• At s~10.6 GeV, (e+e-hadrons) ~3 nb and <Nch> ~8 • Large integrated luminosity (~500 fb-1) can study low-multiplicity exclusive hadronic processes with values ~fb; this provides tests of pQCD at the amplitude level.
PDG 2006
Hadronic cross section
Kai Yi, BaBar/SLAC 3
The BaBar Experimenteecollisions at 10.6 GeV, designed for CP violation in B decays
Different beam energies:Ee= 9.0 GeVEe= 3.1 GeVc.m.-lab boost, =0.55
• Theory calculations (after the measurement) consistent with our results: hep-ph/0606155 hep-ph/0608200 (00)= 21.40.7 17.70.6 fb (0) = 6.00.1 5.60.2 fb
e+e-/--Cross sections
*
*
Kai Yi, BaBar/SLAC 15
e+e-/--VMD model calculation
• Assuming the e+e− → ** process followed by conversion of * into V1 and V2, with effective coupling e/f1 and e/f2 . The cross section in c.m. frame can be written as:
• Obtain effective coupling through meson’s leptonic width:
• Calculation with this simple VMD model agree with our measurements. More calculations based on VMD are summarized in next slide:
M. Davier et al, hep-ph/0606155
Kai Yi, BaBar/SLAC 16
e+e-/--VMD model calculation
• Belle first observed J/ c(cc) at a level 10 times higher than QCD prediction through missing mass recoiling against the J/.
• J/J/ was once proposed to explain the high rate. Its cross section was estimated to be ~ 7 fb, now ~2.5 fb (hep-ph/0608200).
• Not yet observed.
hep-ex/0506062
J/J/
Kai Yi, BaBar/SLAC 17
• TVPA contribution to muon (g-2) is small with the current precision by extending our results to low energy
• Removes a possible uncertainty source in g-2 calculation
• 2/ (pi-rhonium, mixing of and pionium)? 0705.0757[hep-ph]
e+e-/—VMD model calculation
• Discrepancy between decay data and e+e- data as input.
• Interpretation of e+e- cross section ignores C=+1 process.
• How much TVPA contribute? One of our motivations
Eur. Phys. J. 31, 503-510 (2003)Spectral function
R value from e+e-VV(C=+1), |cos*|<0.8, (hep-ph/0606155)
Kai Yi, BaBar/SLAC 18
Observation of ee →
Kai Yi, BaBar/SLAC 19
Observation of ee →
• Single photon (JPC = 1--)
• Other possibility: TVPA (C = +1) followed by FSI → unlikely?
•In general:•C(+-)=(-1)L+S, + or -; •P(+- )= (-1)L;
Single photon productionL odd, S even, I(+- )=1(Bose Statistics).
No angular correlation predictions for this mechanism
u
u
u
u
d
u
d
u
379 fb-1, BaBar Preliminary
Kai Yi, BaBar/SLAC 20
Three independent helicity amplitudes: F00, F10, F11, if one * production assumed.
One QCD model predicts (PRD 24, 2484) s dependence and production angle:
F001/s2, sin*2; F10
<1/s3, 1+cos*2; F11<1/s3, sin*2;
@10 GeV, F00 is expected to dominate.
Test QCD at the amplitude level in helicity structure.
Select:
two tracks: and two good
momentum balance, m < 1.6 GeV/c2
|m - ECM |<280 MeV
ee→—QCD prediction and event selection
Kai Yi, BaBar/SLAC 21
0 m
0 mClear signal for ee →
2D Likelihood Fit in (m-0, m+0 ) plane:
• Signal function= product of P-wave relativistic BWs
• = threshold function
• Linear combinatorial background
Mass projections
ee→—Scatter plot and mass projections
Kai Yi, BaBar/SLAC 22
• We observe 308 ± 25 signal events (> 5). (fiducial) cross section is 8.5±0.7±1.5 fb
(|cos*|<0.8, |cos|<0.85, 0.5<m<1.1)
• Extend to full angular range assuming 1 * production:
(e+e- → 00)>> (e+e- → +-); FSI possible explanation?
• No evidence for Y(4S) → +- .
• e+e-→+- seen in ISR data; e+e-→00 is not seen in ISR as expected.
Will study cross section s dependence using ISR data and this result.
ee→—Cross section
Kai Yi, BaBar/SLAC 23
• Assuming one-virtual-photon (JPC=1- -) production, the total spin S and orbital angular momentum L should satisfy (in L-S coupling):
• *--production angle, * is not well defined (beam depolarization) +--+ helicity angle, +-- + azimuthal angle Similar for -
• Our coordinate system:
e-
*
+
*
+
-
+
+
*
ee→—Coordinate system
Kai Yi, BaBar/SLAC 24
In helicity basis, the decay amplitude of a two-body decay (PRD 57 431, 1998) :
Can be expressed as:
ee→—Angular correlation calculation
Kai Yi, BaBar/SLAC 25
In terms of JP, ee → can be expressed as 1-1-1-, we have the following helicity configurations (,): (1,1), (1,0), (-1,-1),(-1,0), (0,1), (0,-1),(0,0), (1,-1), (-1,1) (angular momentum). The remaining possible amplitudes are: F11, F10, F-1-1, F-10, F01, F0-1, F00
CP conservation
ee→—Angular correlation calculation
i.e. only 3 independent amplitude
Kai Yi, BaBar/SLAC 26
• I~|A|2, complicated angular distribution. Due to low statistics, we only investigate individual angular projection by integrating over the other angles:
• By integrating, we lose strong phase information.
• The most separation power is from dN/dcos. The F00 amplitude contribution goes to zero for =90o .
• The amplitudes are correlated; intensive Toy MC has been done to validate the procedure. No bias is found from Toy MC studies.
ee→—Angular correlation calculation
Kai Yi, BaBar/SLAC 27
• Efficiency corrections to angular distributions: --non-flat dependence of on cos* and cos
--use a 3D(cos*,cos+,cos-) table to correct each event --the method is validated on an independent MC sample.
• Background subtraction using sPlot --weight each event by sWeght obtained from 2D mass fit --consistent with conventional way.
• Weight each event by sWeight and to produce signal angular distributions.
ee→— correction and background subtraction
Kai Yi, BaBar/SLAC 28
ee→—Fit to the projected angular distributions BaBar Preliminary
Helicity angle
Production angle
Azimuthal angleSimultaneous fit to thefive distributions.
F00 dominates but Cannot explain all
pQCD predicted |F00|~=1, and
Non-zero amplitude
|F00| =1
2
00
2
11
2
10 01.0~ FFF
Kai Yi, BaBar/SLAC 29
(syst)00.0(stat)03.004.0
(syst)01.0(stat)04.010.0
(syst)02.0(stat)14.051.0
2
11
2
10
2
00
F
F
F
• Results:
• Fit normalization constraint: 1242
11
2
10
2
00 FFF
|F00|2 ≠ 1, (e+e- → ) > (e+e- → ); no evidence for Y(4S) →
• Are we seeing TVPA + FSI? --Combine with ongoing ISR analysis to measure s dependence of the cross section for each individual amplitudes to investigate FSI.
• Any connection between BVV polarization puzzle and e+e-VV?
ee→—Amplitude result
x4
x2
--Prediction:
--BaBar Data:
Kai Yi, BaBar/SLAC 30
Observation of e+e- at ~10.6 GeV
Kai Yi, BaBar/SLAC 31
• e+e- is analogous to e+e-J/c ( has s-sbar content) Interesting because observed (e+e-J/c ) 10x higher than QCD
predictions • Provides information on s-dependence by combining with a CLEO
measurement at lower energy
• Select:
-- exactly two tracks, identified as K+ and K-
--two good g candidates with deposited energy greater than 500 MeV
--momentum |pK+K-|<0.2 GeV/c in the c.m. frame
-- a pairing with both mK+K- <1.1 GeV and 0.4<m < 0.8 GeV/c2
--select events within 230 MeV of the nominal ECM
Observation of e+e- at ~10.6 GeVPRD (RC) 74, 111103(2006)
Kai Yi, BaBar/SLAC 32
e+e---Signal and scatter plotPRD (RC) 74, 111103(2006)
@ 10.58 GeV @10.58+10.54 GeV
We see correlation. Use a two-dimensional log-likelihood fit to extract signal:P-wave relativistic Breit-Wigner for ; Gaussian resolution function for
Kai Yi, BaBar/SLAC 33
Yield for 1.008<m<1.035 GeV/c2, and 0.4<m<0.8 GeV/c2 :
All data: 245 events @10.58 GeV: 205 @10.54 GeV: 32
Significance: 6.5
U.L. for BF of Y(4S) decay @90% CL based on -10 21 events: 2.5X10-6
Mass projections
e+e---Mass projections
Kai Yi, BaBar/SLAC 34
e+e---Coordinate system• (1--), (0-+), (1--), P conservation L=1, assuming one * production.
• In helicity base, we have only one amplitude: F10. (F00 is forbidden due to vanishing CG coefficient) We have a similar coordinate system:
We ignore the decay angular distributions, they are flat.
e-
*
*
K+
*
Kai Yi, BaBar/SLAC 35
e+e---Angular correlation calculation
Similarly, we can calculate the total helicity amplitude as:
Kai Yi, BaBar/SLAC 36
• Weight isotropic MC angular distributions as above to obtain efficiency estimates.
• The efficiency dependence for each angular distribution is approximately flat, which simplify the correction procedure. • Distributions in data are consistent with predictions within the limited statistics
e+e---Angular distributions
• Due to low statistics, we investigate the angular projections by integrating over the other angles:
Kai Yi, BaBar/SLAC 37
For 1.008<m<1.035 GeV/c2 and |cos*|<0.8 , the cross section after radiative corrections is measured as:
()=2.10.4(stat) 0.1(syst) fb
Extending to (|cos*|<=1) by assuming a 1+ cos2* distribution, this becomes:
()=2.90.5(stat) 0.1(syst) fb
Combine with CLEO measurement at lower energy; 1/s3 energy dependence favored over 1/s4
(pQCD prediction), assuming continuum production.
Analysis of BaBar ISR data is ongoing; see preliminary result next slide.
e+e---Cross section
Recent theory prediction (after the measurement) (hep-ph/0702065): ~3.1~4.3 fb, and 1/s3 dependence favored.
Kai Yi, BaBar/SLAC 38
e+e---Preliminary result from ISR
• BaBar preliminary ISR (ISRKK) result
possible structure(s) near 2.2 GeV
• At “high”-ECM, data (including 10.6 GeV point) are consistent with 1/s4 CLEO measurement seems to be low.
• Dispersion relation phenomenology EPJ A31, 665 (07) --explains the data nicely in terms of ’ and ’ resonances --confirms 1/s4 asymptotic behavior, it is actually helicity F10 amplitude implies that pQCD is right, favor FSI for ee →
BaBar Preliminary
Kai Yi, BaBar/SLAC 39
Connection to LHC
• Angular correlations to determine JPC of X(H) particle --Simple way: assume one configuration, compare to data --General way: assume all configuration, decide the best one.
e.g., X(H)ZZ
• sPlot to subtract background. i.e., HZZ (may not needed)
• Test PYTHIA prediction. Help refine the fragmentation model of PYTHIA for a more precise modeling of the jet content. Even the energy at BaBar is low compare with LHC, but we have information from data.
Kai Yi, BaBar/SLAC 40
SummaryAt BaBar we have:
• Made the first observations of the TVPA hadronic processes: e+e- and e+e- and the angular distributions support TVPA mechanism.
• Observed the process e+e- +-; the measured helicity amplitudes contradict a pQCD expectation at 3.5 , assuming single * production. --Further investigation using ISR data on e+e- +- will provide information on the s dependence and perhaps on understanding of the role of FSI (if any).
• Observed the process e+e- and measured the cross section; this provides an interesting test of the QCD prediction for the energy dependence, assuming continuum production.
• Observed e+e- pp pp, presently being investigated.
Kai Yi, BaBar/SLAC 41
Outlook• We also see evidence of many other exclusive final states. Results from these channels will provide further detailed tests of QCD and hadronization models.
However • B factories provide opportunity to search for new particles. X(3872), Y(4260), Y(4350), Z(4430)+, Y(4660)… (unexplained)
• Z(4430)+, if confirmed, has strong implication for other states.
• May classify them as multiple-quark states, hybrid, glueball,…
• Glueballs and hybrids gain mass through the strong interaction (solely for glueball). A unique place to study: mass creation by strong interaction. (i.e., proton gains only a few percent of its mass through Higgs mechanism) lots of activities are going on…
Kai Yi, BaBar/SLAC 42
Outlook
More fundamental question: How bosons, fermions gain mass? The Higgs mechanism?
• Updated W and top quark masses improved constraint on Higgs mass: MH = 76 ± 31 GeV (mH/mH 39%) (winter 07) LEP limit: >114.4 GeV @95% CL
• New possibilities proposed: --H2aX, a is non-SM particle. (hep-ph/0608310) --CP-Odd NMMSM A0.(hep-ph/0404200, hep-ph/0612031) (put BaBar in the game)
Kai Yi, BaBar/SLAC 43
Outlook
New idea at LHC: Flavor Changing Higgs Decays (FCHDs) BR is estimated to be about 10-4-10-3
• MSSM (h0,H0,A0)bs, Phys. Lett. B 647, 36-42 (2007)
• QCD background free, challenge on s jet identification (impossible?) Trigger possible?• Some ideas on s jet ID (no guarantee to work): --pT of Ks///…? Anything else?hep-ex/9702009, hep-ex/9908038,… --impact parameter separates b (c) from s --Jet charge tagging separates up-type from down-type --use MVA technique to combine?