Abstract No. 1057, Page 1 14

Di Missi g ET Distrib ti at CDF

D e TobackUniver& y of Chicago

for the

CDFCo laboration

DPF ConferenceAugust 11th, 1996

Outline:

Looking at “Diphoton” events at CDF

• Motivation

The ee77T Event

ece t Theoretical Papers

• T e Di oton Dataset and Eve t Selectio

• Mssing ET Evaluation

ector Response to Electromagnetic Events

T Missin ET Distrib tion

• Some Comrneniis on one (set of) SUSY odel(s)

• Co cliisio s

Moti ation:

April 28, 1995 an ee77T

candi ate eve t was recorded

mm

CDII

b—

I(.4

)2

II

Co(.

4)

0()

0CD

/0

rn

CD0

II C’n 0

/rf

lCD

CDiN

)

0 CD1;,

,

Motivation Cont...

Si ce the there have ee a large urn er of theoreticala ers which refer to this eve t.

Ambrosiano et al., Search for Supersymmetry with a Light Gravitino at the Fermilab Tevatronand CERN LEP Colliders hep-ph 96€5398, June 1996

M. Kawasaki et aL, Gravitino Warm Dark Matter Motivated by the CDF ee Event hepph 9607273, July 1996

J. Hisano et L, Is the ee gamma gamma Missing E(T) Event an Evidence of the LightAxino? laep-ph 9607234, July 1996

J. Lopez asidD. Nanopolodos A sjupergravity explanation of the CDFee7-y Event hep ph 9607220,J y 1996

G. Bhattacharyya and R. Moh tr A Non-supersymmetric Interpretation of the CDF e e yyevent hep-ph 96€6408, Juine 1996

Many re ict eve ts wit fi al state of

77T+X

The Dip oton Dataset and Event Selectio

We search events with two photons for anomalous production of events with large T

Specifically, we look at events with two photons with thefollowing properties:

•FT>12GeV

• Central ( < 1.0)

• Isolated

Analysis based on t e CDF dip oto cross section measiireme ts, ut tailored for a searc

his dat was t ken at the er ii b Tev tro at Crug the n 1 t t i erio

The Luminosity for this dataset is 85 pb1

Mis ing ET Evaluation

Systematic problems ca lead to significant measured missi g ET when t ere is o tr e missing e ergy.

• We measure hoton ET well

• We u dermeasure hadronic Jet ETCorrectio s are at the 4 % level

• T e unclustered energy is (on average) u ermeasured

- ev luate th.. Missing ET in a ma ner similar to tiatus d 1 the Top mass analysis. Specifically:

Begin it the r Missin T

Correct or et iismeasureme t usi sta ard C Fjet correctio s

ver 11 correctio for t e unclustere energy

Detector Response to Electromagnetic Events

• We wa t to estimate the detector res onse to electronag etic events

• We compare t e s ape of the Missi g ET S ectr m toe+e eve ts

Drell-Ya as a similar event to ology

• Use the same algorithm as for Di oton events.

We normalize to the dipho on to al event rat

T ue

Photon ET Photon ET

Measured Jet ET

RawMeasured J

True Jet E

Missing energy corrected forets oni

CDF Preliminary

A- iDiphoton candidates 85 pb

ADrell-Yan sample

2 - -

(no masts Ut)

10 caleduptophoton event rate

10

I II I

4-0 10 20 30 40 50 60 70

jet corrected (GeV)

Theoretical Predictions: Light Gravitino ModelAmbrosiano et al., Search for Supersymmetr-y with a Light Gravitino at the Fermilab Tevatron and

CERN LEP CoUiders hep-ph 9605398, June 1996

I ight Graviti o (G) Mo els G = LSF.

---*N1+X and

N1 -÷

0,

Always have 77T + X

4

oaI-

—

— 44 4

4

q

-I

o•

Ea 4

z

60

50

4

‘: ‘.

4’

4

N CC NC• Produc nLf I )

e.g,C1 1+X,N1-4

P> 12GeV

T>SOGeV

=.5 I

P SIL4+

160 200 220

10*

+

60 0 100 120 140 160

C1 (GeV)

240

Conclusions:

• We ave presented a preliminary systematic st dy oft e missi g ET spectr m in diphoton eve ts.

• There are o sig ifica t deviations i the data.

• This measurement lays the groundwork for searc esfor new phenomenon involving diphotons a d missingenergy, as is expected in some SUSY models.