Search for the H0 Dibaryon at KTeV

• Overview• KTeV Detector• Analysis

– Signal Mode

– Normalization Mode

– Transmission Effects

– Lifetime and Branching Ratio

• Results and Future Plans

KTeV Collaboration:Arizona, UCLA, UCSD, Chicago, Colorado, Elmhurst, Fermilab, Osaka, Rice, Rutgers, Virginia, Wisconsin

Ram Ben-DavidFermilab

Rencontres de Moriond /QCDMarch 21-27, 1999

Moriond QCD99 Ram Ben-David

What is the H0 Dibaryon?

• It’s a 6q color singlet hadron:

H0 = (B = 2, S = -2)

• Schematic deuteron wave function:

• Additional flavor possibly lowers the system’s energy through the color-hyperfine interaction:

pnqd 6

2x3q color singlets(long distance, bound by 2.2 MeV)

6q color singlet(short distance repulsion)

NqH 6

Is it stable against strong decays?

uuddss

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Theoretical Predictions for MH

MH

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So What?

• It would be a new form of matter, analogous to mesons and baryons.

• Increase knowledge of strong interactions.

• First of many (?) of multiquark states.

• Astrophysical implications.

M a s s R a n g e L i f e t i m e

2H MM U n s t a b l e

2Hn MMM M e t a s t a b l e : 1S sec1010 -7-10

nHnn MMM M e t a s t a b l e : 2S

days 10

nnH MM C o m p l e t e l y S t a b l e

Moriond QCD99 Ram Ben-David

KTeV Search Region

Recent Experimental Searches

From D. Ashery, Proceedings of Hadron Spectroscopy: 7th Int. Conf. (1997)

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The H0 at KTeV

• Fully reconstruct the final state.

• First analysis to normalize to ’s (S = -2)

– Test coalescense portion of the production model.

• Sensitive to the remaining mass window in

Donoghue et al. model. (PRD34, 3434, 1986)

• Test production at high energies: Rotondo’s model (PRD47, 3871, 1993)

Signal

Mode

Normal

Mode

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Highlights:– 800 GeV/c p on BeO target

– clean and intense beams

– long decay volume

– hermetic detector

– high resolution CsI EM calorimeter

– new DAQ system w/online event filtering

KTeV Spectrometer (Rare Decay Configuration)

GeV 15 E @ % 1 E/E

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Final H0 Cuts

Pt of H0 vs. MH

MH = 2.21 GeV/c2

= 5.28 nsec

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Mass and Momentum Distributions

N

0 0D

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Result

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Test of Donoghue et al. Model

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Sensitivity to Lifetime

Assume BR(H0N) = 100 %

then BR(H0ppp

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Future Plans

• To probe for shorter lifetimes, we need to close the distance between the target and the spectrometer

look for H0’s produced in the regenerator.

• Based on production rate in the regenerator, estimate sensitivity of 100 H0’s per day.

Moriond QCD99 Ram Ben-David

Conclusions

• Ruled out the remaining mass window for long lived H0’s as proposed by Donoghue et al. – Sensitive to the range: nsec <H < 107 nsec

• First test of Rotondo’s production model (at high energies).– Normalizing to ’s is a sensitive probe

of coalescence.

• In KTeV99, we have the ability to search down to 0.5 nsec).

… in addition to the H0, there are some interesting Kaon results.