search for the ν6 particle
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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
.\. 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.
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
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.