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:

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


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


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

Asymmetric detectortrack coverage [/4]~0.92EMC coverage [/4]~0.90

with excellent performance High luminosity:Good tracking, mass resolution ~ 480 fb-1 accumulatedGood , reconstruction. 1.6 billion eeqq evtsGood e,,,K,p ID 0.5 billion eeBB evts

Data sample for today: L~343 fb-1 @10.58 GeV (OnPeak); L~36 fb-1 @10.54 GeV (OffPeak)

Barrel now has LSTs


Data input and physics output

Peak luminosity

(cm-2s-1)

1.201 x 1034

Best shift 329.7 pb-1

Best day 891.2 pb-1

Best week 5.25 fb-1

Best month 18.83 fb-1

BABAR logged

477 fb-1

Run 6

BABAR

Luminosity 477fb-1

Journal Papers 312


Introduction—Processes at B Factories

One photon processes Two photon processes

Two-Virtual-Photon-Annihilation, TVPA; new observation

A subset of e+e-qq processes;or via ISR, a test ground for QCD

B physics

or h

M1

M2

Low multiplicity

~nb

~fb

C= C=+

*

*

*

*

Exclusive hadronic final states

TP

Today’s topic


Observation of e+e-/ (C=+1)


Observation of e+e-/ (C=+1)

PRL 97, 112002 (2006)

@10.6GeV

Select events with invariant mass of (K+K-+-/+-+-) within 170 MeV of c.m. energy.

We are interested in .assume m(0)<2.2 GeV/c2, p*(0)>4.8 GeV/c

Only one entry in the region of interest (no ambiguity)

p*12

p*14

4.8 GeV

No entry

Data


at 10.6 GeV, large kinematic separation between modes...and between “correct” and “incorrect” pairings

e+e-/--generate level simulation


e+e-/--scatter plots in data

signal tiles:0.5<m<1.1 GeV/c2 () 1.008<mKK<1.035 GeV/c2()

Use binned log-likelihood fit over 9 tiles to extract signalIncluding components:KK + + f2(1270) +

Threshold

lego


f2

+- against “” +- against “”

K+K- against “” Correlated and 0 signals

Relativistic Breit-Wigner lineshapes used in the fit

e+e-/--mass projections

f2

totalbackground

background background+f2

total


All Events Yield @

10.58 GeV

Yield @

10.54 GeV

Expected continuum @

10.56 GeV

(from L ratio)

00 124343 >> 5 1138 42 104 14 112 4

0 14713 >> 5 135 13 14 4 13 1

consistent

The extracted signals:

• C parity conservation Y(4S) production do not contribute Consistent with continuum productioncombine On- and Off-resonance data.

• Signals large enough to analyze the angular distributions and investigate the production mechanism for these final states.

• First observation of (C=+1) hadronic final states in e+e- collision. Likely by TVPA.

significanceYield

e+e-/--On-, Off-resonance comparison


e+e-/--TVPA expectation for cos*

where 1

• Production angular distribution due to TVPA:

• Both amplitudes are proportional to inverse of electron propagator:


Production angle *polar angle of or forward in CM consistent with expectation for TVPA

00

H for +

1+cos2* for comparison

e+e-/--Angular distributions in data

Efficiency-corrected projections

sin2H distributions as expectedFor TVPA with quasi-real photon

Helicity angle H—the angle between daughter and recoil in the mother rest frame

0 0

H for +H for K+


• The observed angular distributions support TVPA production:

• The measured cross sections (1.008<m<1.035 GeV, 0.5<m<1.1 GeV, |cos*|<0.8) :

(00)=20.70.7(stat) 2.7(syst) fb reminder: (0) = 5.70.5(stat) 0.8(syst) fb (e+e-hadrons @10 GeV) ~ 3 nb

• 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

*

*


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


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/


• 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)


Observation of ee →


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


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


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


• 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- → +-) = (20.0 ± 1.6 ± 3.6 ± 1.7) fb preliminary (no prediction)

(e+e- → 00) ~ 130 fb hep-ph/0606155

(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


• 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


In helicity basis, the decay amplitude of a two-body decay (PRD 57 431, 1998) :

Can be expressed as:

ee→—Angular correlation calculation


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


i.e. only 3 independent amplitude


• 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.



• 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


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


(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:


Observation of e+e- at ~10.6 GeV


• 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)


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


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


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+

*


e+e---Angular correlation calculation

Similarly, we can calculate the total helicity amplitude as:


• 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:


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.


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


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.


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.


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…


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)


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?

--Topological Vertex help??

Thank you!


Backup—BaBar detector perfomance

Documents

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: