STUDY OF CHARMONIUM STATES IN ANTIPROTON-PROTON ANNIHILATIONS: RESULTS FROM FERMILAB E-835 Giulio Stancari Fermi National Accelerator Laboratory for the.

STUDY OF CHARMONIUM STATESIN ANTIPROTON-PROTON ANNIHILATIONS:

RESULTS FROM FERMILAB E-835

Giulio StancariFermi National Accelerator Laboratory

for the E-835 Collaboration:Fermilab (USA)

INFN and University of Ferrara (Italy)INFN and University of Genoa (Italy)

University of California at Irvine (USA)University of Minnesota (USA)Northwestern University (USA)

INFN and University of Turin (Italy)

IV International Conference on Hyperons, Charm and Beauty HadronsValencia (Spain), 27-30 June 2000

Giulio Stancari Hyperons 2000 Valencia (Spain), 27-30 June 2000 2

EXPERIMENTAL TECHNIQUE

onsannihilati in

formeddirectly be can

states charmonium All

pp

Determination of resonance parameters M, and BIN×BOUT depends on knowledge of beam energy distribution and NOT on detector resolution

To overcome large hadronic background (TOT 70 mb), e.m. final states are used as signature of charmonium formation (OBS pb-nb)


CHARMONIUM SPECTRUM AND ACCUMULATOR


TRADITION TAL EXPERIMEN)cc(pp THE

CERN experiment R704 at the ISR (mid 1980s) proved the feasibility of the technique. Study of the c1 and c2 states...

Fermilab E-760 took data in 1990 and 1991. Precise measurements of c1 and c2 parameters, J/ and ’ widths. Observation of the hc(11P1) state...

Fermilab E-835 (1996/97) was a continuation of E-760. Several detector upgrades (CCAL signal shapers, scintillating-fiber tracker, additional hodoscope…). Some results presented here

E-835 (2000) started data taking last January (till August?). New FCAL, additional fiber tracker, new Accumulator lattice (no transition crossing)… Present status of c0 study shown here


E-835 @ FERMILAB


E-835 DETECTOR

pppp

KKKKpp

spp

eepp

XeeXJpp

moreor 2

/


BEAM, TARGET, LUMINOSITY

Energy distribution of stochastically cooled antiprotons measured from Schottky noise spectrum (f/f 10-7) and closed-orbit length (L/L0 1mm / 474m):

c = f × (L0+L)L0 calibrated at ’

Typical CM energy spread (FWHM) is 500-900 keV


BEAM, TARGET, LUMINOSITY

The variable-density hydrogen-gas jet target allows efficient use of antiprotons and typical instantaneous luminosities of 2.5×1031 cm-2 s-1 (=90 events/nb/hour)

Interaction region, as defined by beam and jet target, is 5×5×7 mm

Luminosity is measured to 3% from pbar-p elastic recoil near 90°


ELECTRON IDENTIFICATION

On-line: two back-to-back charged tracks associated with Cherenkov signal; two back-to-back energy deposits in CCAL with invariant mass > 2.4 GeV

Off-line: Neyman-Pearson test statistic (“Electron Weight”) based upon hodoscope dE/dx, Cherenkov npe and CCAL shower shape

Background mostly due to 0s: photon conversions and Dalitz decays


ELECTRON IDENTIFICATIONTitolo:/usr/users/pallas/OFFE835/NTUPLE/cut_plot.epsAutore:HIGZ Version 1.23/07Anteprima:L'immagine EPS non è stata salvata con l'anteprima inclusa in essa.Commento:L'immagine EPS potrà essere stampata con una stampante PostScript e non con altri tipi di stampante.


STUDY OF THE c0(13P0) RESONANCE

4-10yprobabilitfit Kinematic

1.5;Weight Electron

(CCAL); 6812

);(Cherenkov 6015

clusters; CCAL time-in 4)(or 3

:selectionevent line-Off

θ

θ,ee

1)%27(85.035.090.0

Efficiency selectiongeomtrigger

eeJpp /

Trigger+topology only

Final selection



†Ambrogiani et al., PRL 83, 2902 (1999)

28.19.1 MeV/c2.04.3417

MMeV1.06.16 2.5

7.3 Γ

E-835(96/97)†

eeJpp /

1pb 5.3peak @ L

E-835(2000) PRELIMINARY

far) (so pb 6.12peak @ 1L



42,1c 101)(

QCD massless in forbidden 0)J ,c(c

: tocoupling strong

ppB

pp

pp

41.29.01.18.0

0c

734.028.0outin

108.4

literature from /(

and )/( Using

1009.074.1

pp

-

B

)eeJB

JB

BB


SELECTION OF FINAL STATES

•No in-time extra clusters in CCAL•No undetermined extra clusters forming invariant mass within 35 MeV of 0 mass when paired with candidates•Kinematic fit probability > 5%•Electron Weight < 10-4

Efficiency (75%) estimated for each run

Background comes from 00 and 0 final states with photon(s) outside acceptance or below CCAL energy threshold (“feeddown”). continuum is negligible


STUDY OF THE c(11S0) RESONANCE

pp

E-835(96/97)

MeV1.24.2985 M

E-835 PRELIMINARY



MeV1.21 5.72.6

Gupta et al. (96)Huang et al. (97)

E-835 PRELIMINARY



Huang et al. (97)Münz (96)

Ackleh and Barnes (92)Kroll et al. (93)

Gupta et al. (96)keV 9.3)( 1.81.51.13.1

cE-835 PRELIMINARY


DECAYS OF c0(13P0) AND c2(13P2)

pp

4.0cos



pp



///2,0

2,0

)/(

)(

JbJ

tJ

bt

NN

NN

JB

BR

Decay rates to are measured from the ratio of and J/ cross sections:

B(0,2 J/ ) is relatively well known, compared to statistical error.

Possible systematics from CM energy or luminosity cancel out.



c0c0

c2 c2



keV 033.0049.0270.0)( 2

Huang and Chao (96) Gupta et al. (96)

Münz (96)

Bodwin et al. (95)

Barnes (92)



keV) 65.083.061.1(

CL) (95% keV 47.3)( 0

Münz (96)

Barnes (92) Huang and Chao (96)

Gupta et al. (96)


c1(13P1) AND c2(13P2) ANGULAR DISTRIBUTIONS

eeJpp /1c

) and (or 0 :amplitudesDecay

21 0 :amplitudes Production

1012

110

AAa,a

BB,B

eeJpp /2c

) and ,(or 0 , :amplitudesDecay

and :amplitudes Production

210132

1120

AAAaa,a

BBB



2144 c1 events 95.0cos



6028 c2 events 95.0cos



090.0093.0

2

220 097.0

)(

)0,(

ppB

JppBB

c

zc

50

)0,(

)( therefore

2

0

zJppB

ppB

046003803 0140 ..-.a

Predicted to be 0 or negligibly small (Olsson et al. 1985, Sebastian et al. 1992, Grotch et al. 1984)

Interesting physics. Good test for models



0320031012 0110)( ..-c .a

0490047022 1070)( ..-c .a

31.010.0)(

)(

835E22

12

c

c

a

a

McClary and Byers (1983) predict that ratio is independent of c-quark mass and anomalous magnetic moment

676.0)/(

)/(

35

)(

)(

2

1

theory22

12

JE

JE

a

a

c

c

c

c


CONCLUSIONS

Thanks for your attention!

An interesting physics program is being carried out by Fermilab experiment E-835. Some results have been presented here:

c0 resonance parameters (and more data is being taken as we speak) intriguing coupling to pbar-p

c resonance parameters

c0, c2 and c decay rates to two photons

•angular distribution of c1 and c2 radiative decays c2 magnetic quadrupole component higher than c1

c0 coupling to pbar-p much higher than c2 with Jz=0

STUDY OF CHARMONIUM STATES IN ANTIPROTON-PROTON ANNIHILATIONS: RESULTS FROM FERMILAB E-835 Giulio Stancari Fermi National Accelerator Laboratory for the.

Documents

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present status of c0

cherenkov signal

backtoback energy deposits