achim denig the radiative return: a review of experiments 1 the radiative return: review of...

Achim Denig The Radiative Return: A Review of Experiments

1

The Radiative Return:

Review of Experiments


Review of Experiments

Achim DenigUniversität Karlsruhe

BINP NovosibirskFebruary 27, 2006


2


How and Why?

F

ISR


3

Radiative Return - How?

Modern particle factories, as DANE or PEP-II/KEK-B are designedfor a fixed center-of-mass energy: s = m = 1.02 GeV in the case of DANE,

(4s) in case of B-factories: Energy-scan not possible!

New and completely complementary ansatz: Consider events with Initial State Radiation (ISR)

‘Radiative Return’ to -resonance: e+ e

S. Binner, J.H. Kühn, K. Melnikov, Phys.Lett. B459 (1999) 279

ISR

d(e+ e hadrISR)

dMhadr

for (2m2 < Mhadrs

dhadr +

dMhadr

=

MC- Generator PHOKHARA = NLO

J. Kühn, H. Czyż, G. RodrigoRadiator-Function H(s)

ISR

)(2

2 sdM

dM

H(s) Talk H. Czyż


4

Radiative Return at Particle Factories

[m

bar

n]

1 10

s [GeV]

DANE

Using the method of the Radiative Return one can study the entire energy region below ca. 4 GeV!

PEP-II

s=1.02 GeV

s=10.6 GeV

Experiment KLOE:

Energy region < 1 GeV,

dominated by -channel

(-resonance)

ExperimentBaBar:

Energy region1 ... 3 GeV,

dominated byhigher multi-

plicities (esp. ),up to recently data

with 20 ... 50% systematic errors!

(4s)

pQCD


5

Why Precision Cross Section Measurements?

ahad

<1.8 GeV

Davier, Eidelman, Höcker, Zhang

2m4

had3had ds)s(K)s(

4

1

a

12 - 5 - 12 (+)3.7 - 5 (+J/, )1.8 - 3.743 (+,)2 > 4 (+KK)

• Cross section measurements are of utmost importance for hadronic contribution to muon anomaly ahadr and for knowledge of fine structure constant at s=mZ

2!

Experimental inputinto dispersion integral

2 needed with ca.1% precision!

• Great potential to study the spectrum of vector resonances (J PC = 1 ) above -peak - this region is very poorly known BaBar discovery of Y(4260) resonance (m=42608 MeV, =8823 MeV )

• Production of resonance pairs with limited choice of quantum numbers

Talk J. Izen


6

Results from KLOEat the phi-factory DANE:

The Pion FormfactorHigh Precision needed!


7

Selection ISR

Pion tracks at large angles 50o < < 130o

a) Photons at small angles < 15o and > 165o

No photon tagging

• High statistics for ISR photons• Negligible contribution of FSR• Reduced background

< 150

)pp(pp miss

b) Photons at large angles50o < < 130o

Photon tagging possible• Measurement of threshold region • Increased contribution of FSR • Contribution f0(980)

> 500

The KLOE Detector


8

Small Angle Analysis

ee

m

220

200

180

160

140

120

100

m

0.4 0.5 0.6 0.7 0.8 0.9 1.0.3

MTRK (MeV)

M2 (GeV2)

• Experimental challenge: fight hughe background from ande+ereduced by means of kinematic cuts (trackmass), and likelihood function (e--separation)

• Background from LO-FSR negligible (reduced by acceptance cuts: small ), NLO-FSR not reduced and not a background, efficiency has to be known

• Normalisation to integrated luminosity, which is obtained from large-angle- Bhabha events (clean exp. selection)

LO-FSR NLO-FSR


9

Result Small AnglesAcceptance 0.3%

Trigger 0.3%

Tracking 0.3%

Vertex 0.3%

Reconstruction filter 0.6%

Particle ID 0.1%

Trackmass cut 0.2%

Background 0.3%

Unfolding effects 0.2%

Total experimental Error 0.9%Luminosity ( LA Bhabhas ) 0.6%

Vacuum polarization 0.2%

FSR corrections 0.3%

Radiator function 0.5%

Total theoretical Error 0.9%

TOTAL ERROR 1.3%

(e+e- ) nb

0.4 0.5 0.6 0.7 0.8 0.90.3

200

400

600

800

1000

1200

1400

M2 (GeV2)

KLOE2001 Data

140pb-1

Phys. Lett. B606 (2005) 12

Statistics negligible (1.5 Million events)

Acceptance 0.3%

Trigger * 0.3%

Tracking 0.3%

Vertex 0.3%

Reconstruction Filter * 0.6%

Particle ID 0.1%

Trackmass Cut 0.2%

Background 0.3%

Unfolding Effects 0.2%

Total experimental Error 0.9%Luminosity * 0.6%

Vacuum Polarization 0.2%

FSR Corrections 0.3%

Radiator Function 0.5%

Total theoretical Error 0.9%

*Goal 2002 data: Error < 1%

Normalisatio

n

to µµ

Talk F. Nguyen


10

a [10-10 ]

KLOE (‘05)

SND (’05)

CMD-2 EPS (‘05) preliminary

CMD-2 (‘04)

MM22 (GeV (GeV22))

/

KL

OE -

1

• CMD-2 (‘04) and KLOE agree @ high M

• some disagreement btw. KLOE and CMD-2/SND on the peak

• fair agreement btw all 4 data sets CMD-2 and KLOE agree within 0.5 • disagreement btw KLOE and SND ca.1.5

interpolation of 60KLOE data points from

0.35 to 0.95 GeV2

Comparison with recent e+e Data

Comparison of e+e- experiments 2 contribution to ahadr

[0.3

7-0.

93 G

eV2 ]

JETP, Vol. 101, No 6 (2005) 1053 PLB 578 (2004) 285


11

Analysis 2002 Data: Large Angles

important cross-checkthe threshold region is accessible photon tagging is possible (4-momentum constraints) lower signal statistics large background large FSR (charge asymmetry!)irreducible bkg. from decays

PRO & CONTRA

Talk D. Leone

50o<<130o

50o<<130o

L = 240 pb-1

preliminary

MM22 (GeV (GeV22))

MC MC

By means of dedicated selection

cuts it is possible to fight thedominant background

Threshold region non-trivial due to irreducible FSR-effects,which have to be cut from MCusing phenomenological models(interference effects unknown)

ff

FSR f0


12

• Run at s = 1.00 GeV started on Dec. 16

Good machine performance off-peak:

Status off-peak running Feb. 24, 2006: 167pb-1 written on tape!

DANE - Run Off - Resonance

Dec. 16 Feb. 24Jan. 6

167pb-1

Off-Peak-Performance:

> 5pb-1/day

Intg

erat

ed L

um

inos

ity

/ pb

-1

Feb. 1

XMas

Run-Nr.

• We hope to continue up to end of March and to acquire > 200pb-1

Trackmass [MeV]

Nu

mb

er o

f E

ven

ts /

MeV

10pb-1 ONPEAK

OFFPEAK

Physics Case:• background-free Radiative Return 200pb-1 allow to be statistically competitive with VEPP-2000 at threshold

• a -scan allows to study the model- dependence in desciption of f0(980)

• background-free - program


13

Results from BaBarat the B-factory PEP-II

Higher Multiplicities at higher Energies (so far)I have chosen highlights from published Analyses

3,4,6 Hadrons + pp


14

Radiative Return at BaBar• Center-of-mass energy of machine PEP-II (s=m(4s)=10.6 GeV) far from mass range of interest (ca. < 4 GeV ) requires high energy photon- 5.3) GeV requires high integrated luminosity of PEP-II (Run1-4: ca. 240 fb-1, Goal 2008: 1000fb-1) • Hard ISR-photon back-to-back to hadrons only acceptance for large angle photons photon tagging!

1 muon ID

2 muon IDs

e+e

• Normalisation: to integrated luminosity and radiator function to radiative muon pairs, which are selected with high precision

Event-Display of an ISR-Event in transversal plane


15

• Mass resolution of hadronic system improved by means of a kinematic fit Input to the fit: Momentum and direction of ISR-photon (not energy!) Constraints: energy and momentum conservation (and 0 mass)

• 2-distribution of kinematic fit is the main tool for background subtraction long tail due radiative corrections (NLO) remaining background obtained from MC (for qq events) or from data with sideband technique (for ISR events)

Data +

MC

Radiative Return at BaBar

• Background from (4s) and from B-decays is very small (E > 3 GeV) main backgroud from other ISR-events background from continuum processes e+eqq

Example for 2 distribution from 3 analysis


16

3 Hadrons: e+e

Spectrum dominatedby , , J/ resonances

• Coverage of wide mass region in one experiment: systematic error ca. 5% < 2.5 GeV

• Inconsistency found with DM2 results > 1.4 GeV

• Fit of the mass spectrum up to 1.8 GeV M() = 13502020 MeV/c2 PDG: 1400 - 1450 () = 4507070 MeV 180 - 250 M() = 1660102 MeV/c2 1670 30 () = 2303020 MeV 315 35 M, and phases between and , ’, ’’ fixed in the fit

DM2

BaBar

SND

BR(J/3) = (2.18±0.19)% PDG: (1.50 ±0.20)% BES: (2.10±0.12)%

N=920±34

PRD 70 (2004) 07200489fb-1


17

4 Hadrons: e+e E

vent

s/0.

025

GeV

ISRBackground

Non-ISR Background MC

Average BG fractions

data

Comparison with world data

Systematic errors: – 12% for m4 < 1 GeV,

– 5% for 1 < m4 < 3 GeV, 16% above best measurement above 1.4 GeV

Coverage of wide region in one experiment no point-to-point normalization problems when evaluating (g-2)hadr

PRD 71 (2005) 05200189fb-1


18

Substructures in e+e

J/+-+-

(2S)J/+-

a1(1260)

J/(770)

f0(1370)?

Comparison with Monte-Carlo (Czyż, Kühn): – assumes a1(1260) contribution dominant

– assumes additional f0(1370) contribution confirmed by experiment?!

EPJ C18(2000)497

No J/ in MC

BR (J/ ++)=(3.610.26 0.26)10-3 PDG: (4.0 1.0) 10-3BR ((2S) +J/ )=( 36.11.5 3.7) % PDG: (31.0 2.8) %

Extract J/ , (2S) Branching Ratios:

Channel in preparation!


19

e+e The K+K+ final state The K+KK+K final state

• Large improvement in precision and mass range, in agreement with DM-1

• Systematic error: 15%, domin. Kaon-ID

• Substructures: - dominant K*(892)K - substantial andK+K

• First measurement ever, which benefits from good PID-capabilities

• Systematic error: ca. 25%, few backgr.

BR (J/ K+K+) =(6.090.50 0.53)10-3 PDG: (7.2 2.3) 10-3BR (J/ K+KK+K) = ( 6.71.0 3.1 )10-4 PDG: - no entry -


20

6 Hadrons: e+e 3(The 3(+ final state The 2(+0 final state

• Large improvement in precision • Systematic error: 20%, bkg. dominated • very little substructure: ~1 /event• Dip near 1950 MeV, already seen by FOCUS in diffractive photoproduction

Also first measurement of 2(+K+K

• Hughe improvement in precision and mass range, differences to world data • Systematic error: 20%, bkg. dominated • Very rich substructure: - seen - f0(980), .... present• Dip near 1950 MeV also in this mode

hep-ex/062006 accepted by PRD232fb-1


21

m6=1.88±0.03 GeV

6=130±30 MeV

6=21±40 deg

m420=1.86±0.02 GeV

420=160±20 MeV

420=-3±15 deg

Resonance

Continuum

M3(+-) M2(+-)00

Continuum

Resonance

• Combined fit of continuum and resonance good agreement between charged and partly neutral mode width significantly larger than FOCUS

e+e 3(

2

2

2

2/3

24cont

i

Asims

egm

s

a

msb

contms

eccA

20

)/(

10)(

0


22

2

E2

2p2

M2

2

Gm

m2G

m3

C4)ppee(

2 Protons: e+e p pCross section parametrized by magnetic and electric formfactors GM and GE

• Experimental challenge: fight KK, , bkg. with

10-100 higher cross section• Require 2 good proton

tracks (dE/dx, DIRC)• Perform 3C kinematic fit 4000 pp Events

• Can measure |GE/GM| by fitting the distribution of the cosine of helicity angle• See rise, then fall of |GE/GM|• In disagreement with LEAR data PS170, agreement only at threshold GE and GM equal at high masses

PRD 73 (2006) 012005240fb-1

2pp

pp

K+K

KK

Cut

Mpp

MC from Czyż, Kühn EPJ C35(2004) 527


23

e+e p p

2

2pp

2p

2pp

2

F)m

m21(

m3

C4

Defining the effective proton form factor:

Sharp dips at 2.25 and 3.0 GeVGood agreement

with pQCD-prediction at high Q2

Peak at threshold

Complicated structure is observed:

allows comparisonwith other experiments(ppe+e, e+e pp)

Talks NN


24

Conclusionsand

Outlook


25

Conclusions

• Feasibility of the Radiative Return for high-precision measurement (Pion Formfactor @ 1%) proven at KLOE

• Dedicated DANE-run off-resonance (s=1.00 GeV) with integrated luminosity >200pb-1 will substantially improve precision for tagged and untagged analyses

• Many exclusive ISR channels already measured at BaBar more in progress (K…), welcome BELLE!

Continuous coverage from threshold to Ecm~4.5 GeV Precisions ( 5% ) considerably improved > 1.4 GeV Some channels measured for the first time ever Many J/ψ BR’s better than world average

Clarify confusing situation of Pion Formfactor < 1GeV;Energy region 1 - 3 GeV more and more important for a!

Radiative-Return-Program started in 2000 as work-around

energy scan impossible ! Today established:

complementary & competitive!


26

Reserve


27

140pb-1 Statistics used forthe published analysis(Small angle analysis)

250 pb-1 Data analysis in preparation (small angles & large angles)

Radiative Return at DANE

2004 – 2005 -Run: 2 fb-1


28

dN(/ dM2

after acceptance cuts

Divide by Radiator-function

Radiative corrections

Extract from the Measurement

Differential cross section d()/dM

2

Event-analysis: efficiencies, background

as a function of M

Normalization with Luminosity 10 000

20 000

30 000

40 000

50 000

M [GeV2]

Cross section (e+e- )

Event- Analysis

Excellent mass-resolution

-


29

Ausblick: KLOE • Untersuche Ereignisse bei großen Photonwinkeln, um den Bereich M

2 < 0.35GeV2 zu vermessen, bisher kinematisch unterdrückt!

• Photon Tagging möglich! Komplementäre Analyse mit vollkommen verschiedenen systemat. Fehlern!

• Anteil der FSR groß bei großen Photonwinkeln (bis zu >10%)

Untersuche FSR-Parametri- sierung (z.B. skalare QED) durch Messung der Ladungs-Asymmetrie:

Die Ladungsasymmetrie ergibt sich aufgrund unter-schiedlicher C-Parität der ISR- und FSR-Amplitude

))

)))

(θN(θN

(θN(θNA(θ

ππ

ππ

M2 (GeV2)

P R E L I M I N A R Y

-20K L O E

P R E L I M I N A R Y

Polarwinkel [°]

-10

0

15

10

5

-5

-15

50 70 90 110 130

• KLOE Daten• MC (skalare QED)

Ladungs-Asymmetrie [%]20

-20


30

Komplementäre KLOE-Analyse bei großen Photonwinkeln: 50° < < 130°

• Interferenzterm zwischen ISR und FSR asymmetrisch unter Austausch führt zu einer nicht vernachlässigbaren Asymmetrie zwischen und- :

KLOE: AFB und f0(980), f0(600)

• AFB ist ein sensitiver Parameter auf die Präsenz von skalaren Mesonen f0(980) f0(600) (?)Czyż et al., MC Phokhara, hep-ph/0412239

Vorwärts-Rückwärts-Asymmetrie:

)90(θN)90(θN

)90(θN)90(θN

ππ

FBA

• Dies führt zu einer Ladungs- bzw. Vorwärts-Rück-Asymmetrie für – - Ereignisse

Möglichkeit zum Test der Modell- abhängigkeit der Kopplungen und zum Studium der Natur von f0(980) bzw. Existenz von f0(600)!

0.3

0.2

0.1

0

-0.1

-0.2

0.4 0.6 0.8 1.0M [GeV]

F-B

-Asy

mm

etri

eMC: Nur ISR+FSR+Interferenz, kein f0

KLOE Daten preliminary

MC: Kaon Loop Modell

nur f0(980)f0(980)


31

Hadronischer Beitrag zu a12 - 5 - 12 (+)3.7 - 5 (+J/, )1.8 - 3.743 (+,)2 > 4 (+KK)

< 1.8 GeV

ahad

2[ahad]

<1.8 GeV

<1.8 GeV

Calculations based on hep-ph/0308213Davier, Eidelman, Höcker, Zhang

e+e- data only!


32

Radiative Korrekturen

Radiative Korrekturen:

ii) FSR - Korrekturen Wirkungsquerschnitt inkl. in FSR:

Im Falle des Radiative Return:betrachte - Events mit ISR- und FSR-Photonen = NLO-FSR

i) “Nackter“ Wirkungsquerschnitt dividiere durch Vakuumpolarisation

Vernach-lässigbar!

2 Verfahren für FSR Korrekturen:

• Approach 1: “exklusive NLO-FSR“ - Korrigiere gemessenes für FSR - Benutze MC mit reiner ISR in Analyse - Add. FSR-Beitrag zu (ca. 0.8%)

• Approach 2: “inklusive NLO-FSR“ - Benutze MC mit ISR+FSR in Analyse - korrigiere für Verschiebung in s


33

FSR KorrekturenZwei komplementäre Prozeduren für die FSR-Korrekturen:

“FSR Exklusiver” Ansatz “FSR Inklusiver” Ansatz

N(e+e- ISRFSR)

(e+e- ISR)

(e+e- )

(e+e- ISRFSR )

(e+e- FSR )

Radiator H

Event AnalysePhokhara ISR

Luminosity

Event Aanalyse Phokhara ISR+FSR

Luminosity

Radiator H

FSR

Addiere FSR 0.8 .. 0.9% Schwinger ‘90

subtrahiere FSR Anteil

Wie gut stimmen diese beiden Prozeduren überein?

N(e+e- ISRFSR)


34

FSR-Korrekturen gut verstanden FSR-Beiträge höherer Ordnung vernachlässigbar Faktorisierungs-Ansatz richtig

Pion Formfaktor (KLOE)

= 0.2% ± 0.1%

Unterschied inklusiver -exklusiver Ansatz

0.4 0.5 0.6 0.7 0.8 0.9

1

1.04

1.02

0.98

0.97

0.96

0.95

0.99

1.01

1.03

1.05

1.

FSR Korrekturen


35

Comparison with CMD-2 and - Data

CMD-2KLOE

0.4 0.5 0.6 0.7 0.8 0.9

45

40

35

30

25

20

15

10

5

0

s (GeV2)

Overall good agreement,some deviations in peak?

|F(s)|2 Relative difference e+e- vs.

s (GeV2)

e+e - and – data completely incompatible! Isospinbreaking effects?!

– Data (ALEPH, OPAL, CLEO)error band

differences 10% ... 20%

s (GeV2)0.2 0.4 0.6 0.8 1.0

20%

10%

0%

- 20%

-10%

A. Höcker @ ICHEP04

Pion form factor


36

Muon Anomaly: 2 Contribution to ahadr

= (388.7 0.8stat3.5syst3.5theo) · 10-10

Dispersion integral for 2-channel in energy interval 0.35 <M2<0.95 GeV2

2

2

GeV95.0

GeV35.0

3 )()ππ(π4/1 sKeedsa

Our measurement allows us to compute the contribution of the 2-channel a

in the dispersion integral for the anomalous magnetic moment of the muon.

Comparison with CMD-2 in energy interval 0.37 <M2<0.93 GeV2 :

(375.6 0.8stat 4.9expt+theo) 10-10

(378.6 2.7stat 2.3expt+theo) 10-10

KLOE:

CMD2:

365 370 375 385380

a·1010

Very good agreement in the disperion integral !


37

Muon Anomaly: Theory vs. Experiment

a 11 659 000 ∙ 10-10

Experiment E821

DEHZ’03 [e+e- based]

DEHZ’03 [based]

a 11 659 000 ∙ 1010140 150 160 170 180 190 200 210

a 11 659 000 ∙ 1010

DEHZ‘03

hadrweakQEDtheo aaaa

KLOE- and CMD-2 measurements of the pion form factor are used for a new evaluation of the hadronic contribution and therefore of the muon anomaly!

Comparison experiment - theory allows a precision test of the standard model

Standardmodel prediction: New KLOE measurement Phys. Lett. B606 (2005) 12• New 4th order QED calculation (Kinoshita, Nio) Phys.Rev.D70 (2004) 113001• New ‘Light-by-light’ calculation (Melnikov, Vainshtein) Phys.Rev.D70 (2004) 113006

Theory (SM) - Experiment aexp - atheo = ( 25.2 ± 9.2 ) ·10-10

2.7 standard deviations difference !

CMD-2 and KLOEare averaged in

hadronic contribution

New


38

e+e e+e ISR Y(4260) ISR

In ISR-events in 2005 a new vector resonance was discovered at BaBar:

m = 4260 8 MeV = 88 23 MeV

Why? Hadron Spectroscopy

J/

X = Vector Resonance J PC = 1

125 ± 23 Events

• Direct production allowed only for vector resonances• Resonances with different quantum numbers in decays of vector resonances or in production of vector resonance together with pseudoscalar / scalar

Y(4260)


39

How? Initial-State-Radiation

Rho - Resonanz

0.1 0.3 0.5 0.7 0.9M

[GeV2]

Radiative cross section

a.u

.

Rho - Resonanz

-Resonance

0.1 0.3 0.5 0.7 0.9 s [GeV2]

Non-radiativecross section

a.u

.

MC- Generator PHOKHARAH.Czyż, H.Kühn, G.Rodrigo

Correct for ISR-process

Rho - Resonanz

Radiator function H(s)0.1 0.3 0.5 0.7 0.9

M [GeV2]

a.u

.


40

Background

Mmiss[MeV]

0.6 < M2<0.64 GeV2

DataMC

MC

MC

0.3 < M2<0.34 GeV2

Data

Mmiss[MeV]

Bkg.: Missing Mass

0.62 < M2<0.67 GeV2

Data

MC

MC

MTrk[MeV]

0.32 < M2<0.37 GeV2

Data

MC

MC

MTrk[MeV]

Muon Bkg.: Trackmass


41

DANE - Run Off - Resonance• In Dec.’05 DANE has gone off-resonance

• Scientific Committee of LNF recommends to run at s = 1.00 GeV up to 31/03/06 acquire an integegrated luminosity of 200pb-1

• In addition it was recommended to perform a -scan of 4 points, 10pb-1 each

s (

MeV

)

s = 1023s = 1023

s = 1030s = 1030

s = 1018s = 1018

s = 1010s = 1010

s = 1000s = 1000

Run-Nr.

{

on-peakData 2002

KaonLoop fitNo-Structure fit

(900-1000 MeV), f0(980) dependence on s


42

Overview of (e+e- hadrons)

• CMD-2, KLOE measured (e+e- → -) at <1%.

• Precise (6%) measurements from BES for 2< s < 5 GeV, CLEO data point at 7 GeV.

• No recent data for 1<s<2 GeV, errors ~10-15%.

• CMD-2, KLOE measured (e+e- → -) at <1%.

• Precise (6%) measurements from BES for 2< s < 5 GeV, CLEO data point at 7 GeV.

• No recent data for 1<s<2 GeV, errors ~10-15%.

• R(s) is defined as

• Crucial input for hadronic contributions to – Muon anomalous magnetic moment (a) – Running of QED (for SM fits, Higgs Mass).

• R(s) is defined as

• Crucial input for hadronic contributions to – Muon anomalous magnetic moment (a) – Running of QED (for SM fits, Higgs Mass).

)(

)Hadrons()(

0

ee

eesR

magnitude errors

Burkhardt & Pietrzyk

2001Contributions to

had

Davier et al., 2003

s [GeV/c2]


43

BaBar/PEP-II• PEP-II is an asymmetric e+e- collider with a CM energy of 10.58 GeV.

• Peak luminosity = 9.2 1033 cm-2s-1

• Integrated luminosity = 273 fb-1

BaBar EMC:• 6580 CsI(Tl) crystals• Covers 91% of solid angle• Resolution ~2 % at high E.

Cherenkov Angle(Kaon from D*+ D0 ,

D0 K- + sample)BaBar DIRC•Quartz Cherenkov radiator•Covers 80% of solid angle•Particle ID up to 4-5 GeV/c


44

• Can measure |GE/GM| by fitting the distribution of the cosine of the helicity angle.

• See rise, then fall of |GE/GM|• Not in agreement with LEAR data, except at threshold

1.877<mpp<1.950 GeV

2.100<mpp<2.200 GeV

1.950<mpp<2.025 GeV

2.200<mpp<2.400 GeV

2.025<mpp<2.100 GeV

2.400<mpp<3.000 GeV

pp

M

d

Gd

2cos1~cos

)(

pp

E

d

Gd

2sin~cos

)(

• GE, GM give Different angular distributions:

GE component

GM component

Data + Fit

|GE/GM|

Proton Helicity Angle


45

• Efficiency Corrections– Dependence on |GE/GM|– 2 shape– Nuclear interactions with detector material– PID– photon detection– Triggering

• Cross Section:– No dip at threshold– Sharp dips at 2.25 GeV, 3 GeV

• J/, (2S) signals.• Normalize to e+e- +-

Cross Section

(pb)

PDG

(2.170.08).10-3

(2.36±0.24).10-4

4

3

10)9.03.3())2((

10)16.022.2()/(

ppSB

ppJB

J/ (2S)

Efficiency ME

ME


46

• Define “Effective” form factor by

• Peak at threshold, sharp dips at 2.25 GeV, 3.0 GeV.

• Good fit to pQCD prediction for high mpp.

,3

4 2

2

2

Fm

C

pp

.2 2

2

22

E

pp

pM G

m

mGF

2

2

24 log)( pp

pp

ppM

m

m

CmG

Eff

ecti

ve F

orm

Facto

r

Form Factor

Eff

ecti

ve F

orm

Facto

r

Eff

ecti

ve F

orm

Facto

r


47

e+e- 3(+-)• Same method, Require Ntrk=6• Use 1C Fit, require 2

6 < 20• Same method, Require Ntrk=6• Use 1C Fit, require 2

6 < 20

DataISR Bkg

Efficiency

J/

(2S)

(3(+-)) (nb)

• Efficiency relatively flat in m6, ~20%• Structure at ~1.9 GeV, already in DM2 data.• J/, (2S) signals.• Main source of uncertainty: Bkg subtraction.

• Efficiency relatively flat in m6, ~20%• Structure at ~1.9 GeV, already in DM2 data.• J/, (2S) signals.• Main source of uncertainty: Bkg subtraction.

Non-ISR Bkg

Log Scal

eCovers entire

spectrum up to 4.5 GeV/c2


48e+e- 3(+-) Structures• Simple MC model: only 1 0+-

• Excellent (and suprisingly good!) overall agreement with MC:

– Presence of 0 peak– No other structures in 2, 3, 4 spectra

• Signal from J/ S[not in MC]

3.15 < m6 < 4.5 GeVm(+-)

m(+-

)

m(2+2-

)

J/

(2S), including +- J/

Data MC

Charmonium

states not

included in M

C

GeV/c2

GeV/c2

GeV/c2


49e+e- 2(+-) 00Data ISR

Bkg

Non-ISR Bkg

Cross Section (nb)

Efficiency

Shape similar to 3(+-); differs sharply from DM2 above 1.9 GeV/c2

but other measurements very imprecise.

Shape similar to 3(+-); differs sharply from DM2 above 1.9 GeV/c2

but other measurements very imprecise.

• Require E > 50 MeV, cut on helicity• Require Kaon veto for charged pions• Use 5C fit (impose 0 masses, exclude

Energy)

Log Scal

e


50e+e- 2(+-) 00 Structures• Rich resonance structure:

–

– f0– f2(1270)/f0(1370)?– J/2(+-) 00

Data in Red, MC in Blue

f

in Red, ½(

in Blue

f(1270) or f(1370)

J

m()

No f0


51e+e- 2(+-) 00 Structures (2)

A signal for e+e- , is visible

A signal for e+e- , is visible

Select

in other

combination

2

02

02

2/32

0 )(

)(

sims

m

mF

sF

s

m

F(s) = 2-body P-wave

phase-space

Fit Results:

0 = 3.08±0.33 nbm = 1645 ± 8 MeV= 114 ± 14 MeV

Fit Results:

0 = 3.08±0.33 nbm = 1645 ± 8 MeV= 114 ± 14 MeV

(1680) ?

(1650) ?

J/

J/

(2S)

(e

+e

-

)

(n

b)

Fit a resonance shape: Fit a resonance shape:

m = 1680 ± 20 MeV, = 150 ± 50 MeVm = 1670 ± 30 MeV, = 315 ± 35 MeV


52

e+e- K+K-2(+-)• Same as before, + Require 2 Kaons.• Clear signals for K*0, J/and (2S)• signal in K+K- spectrum, some from J/

decays.

• Same as before, + Require 2 Kaons.• Clear signals for K*0, J/and (2S)• signal in K+K- spectrum, some from J/

decays.J/

(2S)

J/

(2S)

K*0

J/

K*0

(K+K-2(+-)) (pb)

Band


53

J/ Results for 6h Modes

But for 3(), only 1excess, not enough for BF value. But for 3(), only 1excess, not

enough for BF value.

Mode BaBar BF (232 fb-1) PDG 2004

J33 (4.40±0.29±0.29)10-3 (4.0±2.0)10-3

J22 (1.65±0.10±0.18)10-2 n/a

J (1.47±0.41±0.15)10-3 (1.58±0.16)10-3

JK+K-22 (5.09 ±0.42±0.35)10-3 (3.1±1.3)10-3

J22 (1.77 ±0.35±0.12)10-3 (1.60±0.32)10-3

Mode BaBar BF (89.3 fb-1) PDG 2004

(2S)22 (5.3±1.6±0.6)10-3 n/a

(2S)K+K-22 (2.1 ±1.0±0.2)10-3 n/a

33

K+K-22

22

Can remove J/(4), get direct signal. Can remove J/(4), get direct signal.


54

e+e- +-+-• Perform 1C kinematic fits with m = 0 for 4, 2K2, 4K hypotheses

• Identify kaons using Cherenkov angle and dE/dx.

even

ts/0

.025

GeV

(~60K evts)

ISRBackgroun

d

e+e- +-+- Cross Section

(89.3 fb-1)

Non-ISR Background MC

Average BG fractions

data


55

Resonant Structures in e+e- +-

+-

M(GeV/c2)

Charmonium

states n

ot

included in

MC

Data MC

J/+-+-

(2S)J/+-

(2S) excluded from these plots

f2(1270) or f0(1370) ?

MC

M4 = 2.3-3.0 GeV

MC

Data

f2(1270) or f0(1370) ?


56

e+e- K+K-+-• Require 1 or 2 Kaon IDs• Negligible background• Good agreement with

DM1, much higher ECM reach.

• Systematics: Kaon ID, Efficiency.

• Require 1 or 2 Kaon IDs• Negligible background• Good agreement with

DM1, much higher ECM reach.

• Systematics: Kaon ID, Efficiency.

e+e- K+K-+-

Cross Section (89.3 fb-1)


57

e+e- K+K-+-Resonant Structures

• K*(892) K dominates

• No K*K*, DD signals.

• , in K+K- and spectra with K*(892) bands excluded

• K*(892) K dominates

• No K*K*, DD signals.

• , in K+K- and spectra with K*(892) bands excluded

Excluding the K*(892) bands

band

K*0

No obvious structure in +-

when selecting K+K-

No obvious structure in +-

when selecting K+K-


58

B((2S) J(36.1±1.5±3.7)B((2S) J(36.1±1.5±3.7)

• (2S) in 2+2- mode is signal is actually J/, no direct signal seen.

• Assuming PDG value of (2S)e+e-) and B(J/ ),

Assume PDG value of Je+e-): Assume PDG value of Je+e-):

PDG: 31.02.8 %)%8.25.11.36()/)2(( JSB

Would be interesting to compare with 00J/ BF from e+e- +-

00... Work in progress!

Mode BaBar BF (89.3 fb-1) PDG 2004

J (3.61±0.26±0.26)10-3 (4.0±1.0)10-3

JK+K- (6.09±0.50±0.53)10-3 (7.2±2.3)10-3

J2K+2K- (6.7 ±1.0±1.1)10-4 n/a


59

e+e- +-0

NJ/ = 92034

Cross-Section:• Overall normalization error

~5% below 2.5 GeV.• Consistent with SND data

for M3 < 1.4 GeV.

• Inconsistent with DM2 results.• Structures at 1.25 and 1.65 GeV,

fit to and ’’, assuming:•(’) – () = 1800.•(’’) – () = 00

Cross-Section:• Overall normalization error

~5% below 2.5 GeV.• Consistent with SND data

for M3 < 1.4 GeV.

• Inconsistent with DM2 results.• Structures at 1.25 and 1.65 GeV,

fit to and ’’, assuming:•(’) – () = 1800.•(’’) – () = 00

M3[GeV/c2]

SND

J/

DM2

BaBar PDG 2004 BES 2003

B(J/) (2.18±0.19)% (1.50±0.20)% (2.10±0.12)%

PDG: 1400-1450 MeV/c2

PDG : 180-250 MeV

PDG: 1670 ± 30 MeV/c2

PDG: 315 ± 35 MeV

MeV 2030230

MeV/c 2101660

MeV 7070450

MeV/c 20201350

''

2''

'

2'

M

M

MeV 2030230

MeV/c 2101660

MeV 7070450

MeV/c 20201350

''

2''

'

2'

M

M

BaBar124 fb-1

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