search for the ν6 particle

4
im iiii I I1' -~- PROCEEDINGS SUPPLEMENTS Nuclear |'hys~c.~ |3 (Pro¢, Suppl.) 25~ (19~) 48-51 North-Ho|la:~d SEARCH FOR THE ~6 PARTICLE * The CDF ColIabom~** Presented by Nikos GIOKARIS The Rockefeller University, New Ymk, New York I00H-6399 The 116particle is a sextet quark pseudoscalu state proposed to explain the high p value me~ured by the UA4 experiment at CERN and the Mini-Centaum and Geminion events of cosmic ray experiments. W~ have searched for the q6 decaying into two photons in the 1988-89 CDF data. in this report we describe the analysis and present limits on the q6 production cross ~tiofl dines branching ratio into two p h o ~ . 1. INTRODUCTION The UA4 experiment at the CERN collider has measured I the real over imaginary past of the forwasd elasdc scattering amplitude (the p value) and obtained an unexpectedly high value. Aho, the total plylr-p crois section dce~ not clu~ge very much in going from CERN toFNAL collider energies 2. These two facts lead K.Kang and A. White to propo~3 the existence of a Rxtet quark state, called q6, with a m~s of 30+-10GeV. For some fime now, several theorists have strongly ad~ocated an electroweak symmew/b,c~.ing scheme in which the usual Higgs sector of the standard model is replaced by a flavor doublet of color sextet quarim4,,5,6,7,8,9. K~g ".nd White ~in~ Out that the Mini~Centauro and Geminion cosmic ray cventslO, 11 could actually be identified as the hadronic and the two photon decay products of the q6, respectively. The ~reshold Center of Mass energy is estimated to be around 450 GeV, slightly below the SIS collider energy. The ~6 is supposed to be produced diffractively with a very high cross ~ction ( several mb at 1800 GeV) and the branching ratio of its decay mode into two photons is ;wice that into hadrons. The mass, the diffracdve production nature and the decay branching ratios *Work in progress. **The collaborating institutions are listed in O~ Appendix. of the I16 me forced upon the model by the characteristics of the Mini-Contauro and the Geminion events. The large value of its production cross section is needed to fit simultaneously the p value at 540 GcV and the total cross section in the CERN SPS to FNAL TEVATRON energyrange. Production of 116 is possible at high energy e + e" colliden.I", Hatsuda and M. Ume~wa have proposed 12 a way to search for the lq 6 in Z0 radiative decays at LEP~ They estimate the F(Z 0 ->yrl6)IF(zO ->P+W) ratio to be of the order of 10 "S. 2. DATA ANALYSIS Because of background considerations, we have limited our search for the q6 to the two photon decay mode. The diffractive production of the lq6 results in "lopsided" events, with two photons at high rapidity on one side of the detector, and no enemy deposition on the other side. This rapidity topology does not rue the CDF level zero trigger, and is therefore not included in the standard CDF data stream. However, the large (theoretical) production

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Page 1: Search for the ν6 particle

im iiii I I1' - ~ -

PROCEEDINGS SUPPLEMENTS

Nuclear |'hys~c.~ |3 (Pro¢, Suppl.) 25~ (19~) 48-51 North-Ho|la:~d

SEARCH FOR THE ~6 PARTICLE *

The CDF ColIabom~**

Presented by Nikos GIOKARIS

The Rockefeller University, New Ymk, New York I00H-6399

The 116 particle is a sextet quark pseudoscalu state proposed to explain the high p value me~ured by the UA4 experiment at

CERN and the Mini-Centaum and Geminion events of cosmic ray experiments. W~ have searched for the q6 decaying into

two photons in the 1988-89 CDF data. in this report we describe the analysis and present limits on the q6 production cross

~tiofl dines branching ratio into two p h o ~ .

1. INTRODUCTION The UA4 experiment at the CERN collider has

measured I the real over imaginary past of the forwasd elasdc

scattering amplitude (the p value) and obtained an

unexpectedly high value. Aho, the total plylr-p crois section

dce~ not clu~ge very much in going from CERN to FNAL

collider energies 2. These two facts lead K.Kang and A.

White to propo~3 the existence of a Rxtet quark state, called q6, with a m~s of 30+-10GeV. For some fime

now, several theorists have strongly ad~ocated an

electroweak symmew/b,c~.ing scheme in which the usual Higgs sector of the standard model is replaced by a flavor doublet of color sextet quarim4,,5,6,7,8,9.

K~g ".nd White ~in~ Out that the Mini~Centauro and

Geminion cosmic ray cventslO, 11 could actually be

identified as the hadronic and the two photon decay products of the q6, respectively. The ~reshold Center of Mass energy

is estimated to be around 450 GeV, slightly below the SIS collider energy. The ~6 is supposed to be produced

diffractively with a very high cross ~ction ( several mb at

1800 GeV) and the branching ratio of its decay mode into

two photons is ;wice that into hadrons. The mass, the

diffracdve production nature and the decay branching ratios

*Work in progress. **The collaborating institutions are listed in O~ Appendix.

of the I16 me forced upon the model by the characteristics of

the Mini-Contauro and the Geminion events. The large value

of its production cross section is needed to fit simultaneously

the p value at 540 GcV and the total cross section in the

CERN SPS to FNAL TEVATRON energy range.

Production of 116 is possible at high energy e + e"

colliden. I", Hatsuda and M. Ume~wa have proposed 12

a way to search for the lq 6 in Z 0 radiative decays at LEP~

They estimate the F(Z 0 ->yrl6)IF(zO ->P+W) ratio to be of

the order of 10 "S.

2. DATA ANALYSIS

Because of background considerations, we have

limited our search for the q6 to the two photon decay

mode. The diffractive production of the lq 6 results in

"lopsided" events, with two photons at high rapidity on one

side of the detector, and no enemy deposition on the other

side. This rapidity topology does not rue the CDF level zero

trigger, and is therefore not included in the standard CDF

data stream. However, the large (theoretical) production

Page 2: Search for the ν6 particle

.\. GFokaris/Search for the vc, particle ,19

the beam crossing. Therefore the data collected thi~ way

have no trigger bias at all.

We have looked for the "q6 in such a run. The three main

elements in the analysis are: (a) Use the standard CDF

offline calorimeter clustering algorithms and count the

number of events with one or more electromagnetic clusterr

with E T > $ GeV. (b) Find the integrated luminosity of the

LOQuery run. (c) Construct a Monte Carlo for a diffractively

produced 116 decaying into two photons. The Monte Carlo

events are then analyzed with the CDF calorimeter

simulation programs to obtain acceptances and detector

efficiencies.

2.1. EM Clusters

The first pass through the raw data selected events

with one or more energy clusters. This requirement reduced

the number of events from a total of 16,992 to 2417. The

second pass searched for events with electromagnetic energy

clusters with ET>SGeV and HAD/EM ratio of less than 0. i.

No other cuts were required, so that both electrons and

photons 0t 0) were accepted. We ended up with 31 events

with one or more electromagnetic clusters. The 31 events

contained dO e~tromagnetic enemy clusters and were hand

scanned. Most of these clusters appeared over a very small

period of 't, me during the run and were identified as

electron/.c noise ~ 3. Ne genuine electromagnetic clusters,

passing the above cuts, were found in the forward region

where one expects to detect'~s from 116 decay3"

2.2. Integrated Luminosity

The CDF luminosity module was used to identify events

with one or more interactions. There are 3277 such events in

the analyzed run which, for an effective Beam-Beam counter

cross section 14 of 46.8+-3.2 mbarns, has an integrated

luminosity of 70+-$ (mharns)-1. This number is corrected

for multiple interactions - a 10% correction at this

luminosity.

existing CDF miqLm_um bias Monte Carlo) has been

modified. We take the simplest possible model where the

beam proton (antiproton) transforms, through the exchange

of a pomeron, into an object (X) with a mass equal to the

sum of the proton and 116 masses (we have considered "q6's

in the mass range 15 to 40GeV). The transverse

momentum distribution of the X behaves like e bt, where

the slope b is taken 15 to be 12 (GeV/c) -2. This object

decays into the T16 and a proton (antiproton). The beam

momentum (900 GeV/c) is divided bet~veen the 116 and the

proton (antiproton) proportionally to their masses. In its

center of mass the 116 (a pseudoscalar state) decays

uniformly into 2 photons. The momenta of the two photons

are subsequently transformed into the Lab system. The

whole 116 production and decay into two photons chain is as

follows:

pbar ~ p . . . . >pbar + X

l >'q6 + P

l -> 77

The photons have relatively high PT but they are dis~bute~

close to q = 4 (edge of the CDF detector).

After the detector ~imulation the standard CDF

electron/photon analysis modules are used to analyze these

events exactly the same way as real data. The detection

efficiencies for one or both photons, as a function of the ~6

mass, are listed in Table I and plotted in Figure 1. The ET

of the photon(s) was required to be greater than 5 GeV. The

two photon efficiency is zero for eta-six masses below 35

GeV.

Page 3: Search for the ν6 particle

l .~O;~aFtS / D~aFCII l o t ".-*l]e ~t6 pO. l ~,t~.L~

E~a - six ..m~.ass C.,ne p.'.~.t~.. Two Photons

(GeV) (%) (%)

20 0.26+-0.02 <0.006

22 3.08+-0.17 < 0.03

25 16.7+-0.4 < 0.03

30 49.6+-0.2 <0.03

36 77.1+-0.2 0.02+-0.006

38 82.3+-0.2 0.50+-0.03

40 85.2+-0.4 2.31+-0.15

45 88.8+-0.4 13.6+-0.5

50 88.6.-0.4 24.0+-0.6

55 88.1 +-0.4 32.1 +-0.7

3. P--ESL~TS -CONCLUS[ON

nl.o/f~rwsrd me,inn Althrm~,h there are ~3 event; in the

centrai calorimeter, thece is no acocptmc¢ in this region f~r a

diffractively produced 116 decaying into two photons.

Therefore we conclude that we observe no events with a

topology consistent with the model of reference 3. Siace no

events have been obscwed, we ~-'a]culat¢ the 95% CL upper

limit for (~. Br (pbar-p . . . . >116 . . . . . >2"1') as :

~ . B r = ( 3 / 70 mb' l .¢ )

where ~ is the detection efficiency.

This is plotted in Figure 2 along with the prediction of

reference 3. Using the one photon selection curve our data

pretty much exclude "q6's in the mass range and cross

section level predicted 3.

1 0 0

8O

v e) 60 O

,0 ¢J o

CDF Work in Progress

0 0

o - I~. ecle©tion (gT • 5 GeV) x - 27 lelectlor~ (F.~ > 5 GeV) 0 0 Q ' ' " 0 ". •

o

Ftdu©iel cut for ?'l 00S i l q l~ l .O • 1,2 II~IS~.2 2.4 ~l~IS3.e ."

.x

x

0 x

I 19" 1 t . I I O 20 30 40 50 60

M ( n e) ( G e V / d )

tO 3

,o~ ,Q

" ~ I0 I C.)

tn

"~ toe m 4 b

16-1

10-2

CDF Work in Progress

o - 17 selection ( ~ • 5 GeV) x 2? select ion (r., > 5 GeV)

o

-, ,]"

i " - I(Iml-Whlte Model x (M - -<lOt16 GeV)

!

k

"0 X " x

O , "" 0 0 0 0 . 0 ' 0

. . . . I . . . . [ i . . . . i . . . . ] , , , t

zo 20 ~o 40 so so M(~e) (GeV/c 2)

FIGURE 1

116"'>~ acceptance

FIGURE 2

O(•6 "->W) upper limit

Page 4: Search for the ν6 particle

N. Giokaris /Search for the Ti6 partiNe 51

Fh's o:.'erk :va~. c:-~ed e~at ie e;.c,=zr~tL.., w:fh ~--

c,Aicagues mark i imko and ~eruio Kamon. we would like ,_o u:._-~ MJlci~_des ,Co.m"n"~'=~ . . . . -,,- checNng our iurranosity estimate and Konstantine Goufianos for reading this note and

making many useful suggestions.

APPENDIX

Argonne National Laboratory, Brandeis University,

University of Chicago, Fermi National Accelerator Laboratory, INFN,Fraseati-Harvard University-University

of Illinois-National laboratory fo High Energy Physics

(KEK)-Lawrence Berkeley Laboratory-University of

Pennsylvania-INFN, University and Scuola Normale,

Pisa-Purdue University-Rockefeller University-Rutgers

University-Texas A&M University-University of

Tsukuba-University of Wisconsin.

5. E. Braaten et al, J. Mog. Phys. A1 (i986) 693.

7. Po Forgas and G. Zoupanos, Phys. Left. !48B

(1984) 99.

8. G. Zoupanos, Phys. Lett. 129B (1983) 315.

9. D. Lust, E. Panagiotopoulos, K. Streng and G.

Zoupanos, Nucl. Phys. B268 (1986) 49.

10. S. Hasegawa, Fermilab CDF Seminar ICR-Report No.

151-87-5, 1987 (unpuplished).

l l .Chacaitaya and Pamir Collaboration, ICRR-

Report-232-91-1.

12,T. Hatsuda and M. Umezawa, Phys. Lett. 254B,

(1991) 493.

REFERENCF~

1. Bernard et al., Phys.Lett. B 198 (1987) 583.

2. N.A. Amos et all., Phys. Rev. Lett. 243 (1990) 158.

3. K. Kang and A.White, Phys. Rev. D42 (1990) 835.

4. W.J. Marciano, Phys. Rev. D21 (1980) 2425.

13. N. Giokaris, T. Kamon, M. Timko, "Search for the 116

Particle", CDF Note # 1437.

1 4 . C . O . Pilcher and S. White, "CDF Luminosily

Calibration", CDF Note # 1202.

15. S. Belforte and K. Goulianos, "A Complete Minimum

Bias I~ven[ Generator", CDF Note # 2~6.