ABRAMS, GS

AMIDEI, D

BLOCKER, CA

BOYARSKI, AM

BREIDENBACH, M

BURKE, DL

CHINOWSKY, W

DELAVAISSIERE, C

DIETERLE, WE

DILLON, JB

DORFAN, JM

EATON, MW

FELDMAN, GJ

FRANKLIN, MEB

GIDAL, G

GLADNEY, L

GOLD, MS

GOLDHABER, G

GOLDING, LJ

HANSON, G

HOLLEBEEK, RJ

INNES, WR

JAROS, JA

JOHNSON, AD

KADYK, JA

LANKFORD, AJ

LARSEN, RR

LECLAIRE, B

LEVI, M

LOCKYER, N

LUTH, V

MATTEUZZI, C

NELSON, ME

PATRICK, JF

PERL, ML

RICHTER, B

ROWSON, PC

SCHAAD, T

SCHELLMAN, H

SCHLATTER, D

SCHWITTERS, RF

SHELDON, PD

STRAIT, J

TRILLING, GH

YELTON, JM

ZAISER, C

eScholarship - University of California

UC IrvineUC Irvine Previously Published WorksTitleLIMITS ON J/PSI-PRODUCTION AND UPSILON-PRODUCTION IN E+E-INTERACTIONS AT SQUARE-ROOT-S=29 GEVPermalinkhttps://escholarship.org/uc/item/03x9x6f7JournalPHYSICS LETTERS B, 129(1-2)ISSN0370-2693AuthorsMATTEUZZI, CABRAMS, GSAMIDEI, Det al.Publication Date1983DOI10.1016/0370-2693(83)90745-1Copyright InformationThis work is made available under the terms of a Creative Commons Attribution License, availalbe at https://creativecommons.org/licenses/by/4.0/ Peer reviewedeScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaVolume 129, number 1,2 PHYSICS LETTERS 15 September 1983 LIMITS ON J / ~ A N D  T PRODUCTION IN e+e - INTERACTIONS AT X/s= 29 GeV ~ C. MATTEUZZI, G.S. ABRAMS, D. AMIDEI, C.A. BLOCKER, A.M. BOYARSKI, M. BREIDENBACH, D.L. BURKE, W. CHINOWSKY, W.E. D1ETERLE 1, J.B. DILLON, J.M. DORFAN, M.W. EATON, G.J. FELDMAN, M.E.B. FRANKLIN, G. GIDAL, L. GLADNEY, M.S. GOLD, G. GOLDHABER, L.J. GOLDING, G. HANSON, R.J. HOLLEBEEK, W.R. INNES, J.A. JAROS, A.D. JOHNSON, J.A. KADYK, A.J. LANKFORD, R.R. LARSEN, B. LeCLAIRE, M. LEVI, N. LOCKYER, V. LI]TH, M.E. NELSON, J.F. PATRICK 2, M.L. PERL, B. RICHTER, P.C. ROWSON, T. SCHAAD, H. SCHELLMAN, D. SCHLATTER, R.F. SCHWITTERS, P.D. SHELDON, J. STRAIT 3, G.H. TRILLING, C. de la VAISSIERE, J.M. YELTON and C. ZAISER Stanford Linear Accelerator Center, Stanford UniversiO,, Stanford, CA 94305, USA Lawrence Berkeley Laboratory and Department o f  Physies, University of  California, Berkeley. CA 94720, USA Department o f  Physics, Harvard University, Cambridge, MA 02138, USA Received 29 April 1983 A search has been made for the inclusive production of J/¢, (3.1) and T (9.4) mesons in e+e - interactions at 29 GeV, via their decay into two leptons. No signal is observed in the J/O region, nor in the "r region. The limits on the cross sec- tions are o (e+e - ~ ~X) < 4.4 X 10 -36 cm 2, and o (e+e ~ TX) < 4.7 × 10 -36 cm 2. The same data yield limits on the branching ratios for the b quark BR (b -~ +X) < 4.9% and BR(b --* Q+~-X) < 0.8%. In this letter we present a search for inclusive production by detection of the dilepton decay mode: + - -  e e  -+~X L p+#-,  e+e - (1) at a center-of-mass energy of 29 GeV using the SLAC- LBL Mark II detector at the PEP storage ring. Both leptons in ( l )  were identified either by the muon sys- tem or by tile electromagnetic shower calorimeter, exploiting the good efficiency of the apparatus for detecting both muons and electrons. A similar search was carried out for T production. No signal for the J /~ or "P was found and we give upper limits on the inclusive production cross sections. ":~ Work supported in part by the Department of Energy, con- tracts DI.;-AC03-76SI:O0515, W-7405-ENG-48, and DE- AC02-76ER03064. 1 Present address: University of Arizona, Tucson, AZ 85721, USA. 2 Present address: l:ermilab, Batavia, IL 60510, USA. 3 Present address: University of Massachusetts, Amherst, MA 01002, USA. Various dynamical mechanisms suggest that obser- vation of the ~ may be a good signal for underlying new physics. For example, in heavy quark decay, a decay sequence leading through charm may provide a c~ bound state some reasonable fraction of the time [ 1 ]. The initial heavy quark could result either from direct coupling to the intermediate virtual photon, or be coupled to a Higgs particle or to some other exotic system. Several QCD predictions have also been made for ~ production [2]. The perturbative calculations for the inclusive process e+e - -+ ~X yield cross sec- tions between 10 -3  and 10 -4  ous t for Ecm > 15 GeV. Very high statistics experiments are needed in order to check these calculations and to identify the differ- ent mechanisms which are involved. The perturbative calculations are however the minimal expected con- tribution to $ inclusive production: a large uncer- tainty comes from possible non-perturbative contribu- tions. Some calculations [3] predict a cross section larger than 10 -1 ouu , which would imply a large prob- ability to observe $'s  at energies Ecru > 15 GeV. In the inclusive $ production e+e - -+ SX, the ~ leptonic 0 031-9163/83/0000 0000/$ 03.00 © 1983 North-Holland 141 Volume 129, number 1,2 PHYSICS LETTERS 15 September 1983 decay modes should stand out relatively cleanly above a background of  uncorrelated e+e - o r / l + / i  pairs. The detector  has been described elsewhere [4]. Charged particles are detected over 80% of  the solid angle with a cylindrical, 16 layers, drift chamber. The solenoidal magnetic field is 4.6 kG for 43% of  the data sample and 2.3 kG for the remaining 57%. The average momentum resolution is 2xp/p = [(0.015) 2 + (0.007 p)2] 1/2 (where p is in GeV) when the particle is constrained to pass through the beam interaction point. The smaller magnetic field was compensated for by the installation of  a vertex detector  in the sum- met 1981, which provides improved spatial resolution for charged particle tracking. Outside the magnet coil there are 8 lead-liquid argon shower counters which serve to identify and measure photons and electrons over 65% of  the solid angle. The detector  is surrounded by four layers of  steel plate absorbers and proport ional  tubes, used to identify muons over 55% of  the solid angle. A particle is identified as a muon if  it traverses at least three layers of  the absorber and has a range con- sistent with that expected for a/a. At  each layer the associated hits must be within 3 standard deviations of  the extrapolated trajectory. This selection requires a minimum muon momentum of  1.4 GeV/c. The prob- ability that a hadron within the nruon system solid angle fakes a muon by decay or punch through within these criteria is less than 1.1%. An electron is identi- fied from the amount of  energy deposited in each layer of  the liquid argon calorimeter. The total energy and the shape of  the shower inside the calorimeter is examined for each track [5]. The identification effi- ciency is ~76% at 1 GeV and increases with the elec- tron energy. The probabil i ty of  misidentifying a ha- dron as an electron depends on its position inside a jet  of  particles, and is typically 1%. In the search for ~ 's ,  a sample of9411 hadronic events is selected out of  a total luminosity of  34 617 nb -1  with the following cuts. Each particle must have R < 5 cnr and Z < 10 cm, where R and Z are the dis- tances of  closest approach to the interaction point in a plane perpendicular to and along the beam axis respectively. Each event has the following properties: (1) There must be 5 or more charged particles each with momentum p > 0.1 GeV/c. Dividing the event in two hemispheres with respect to a plane perpendicular to the sphericity axis, there must be at least 2 charged particles in each hemisphere. (2) The sum of  the magnitudes of  the charged par- ticle momenta  must be greater than 7.5 GeV/c. (3) The sphericity [6] axis must form an angle 0 s with the beam such that I cos 0 s I < 0.7. Requiring that two leptons be detected,  we are left with a sample of  250 events. The invariant mass is computed for all neutral pairs of  leptons of  the same type,  if at least one of  them has a transverse momentum with respect to the sphericity axis larger than 1 GeV and both leptons have momenta  ranging between 1.4 and 11 GeV/c. Fig. 1 shows the invariant mass distribution for oppo- site charge e+e - and/a+/~ - combinations. There are no events in the region between 2.5 and 3.3 GeV, corre- sponding to the position of  the 4- The background is estimated by a Monte Carlo method.  A simulation of  e+e - ~ q~ and e+e - -~ qqg, including radiative effects, was used to describe the data from e+e - -~ hadrons. The Monte Carlo simula- tion agrees well with the data for the distributions in momentum and transverse momentum of  the leptons, for the charged multiplici ty,  etc. The source of  leptons in the Monte Carlo is mostly the semileptonic decay of  c and b quarks, with a small contribution from 7r and K decay and from 7's converting in the material close to the interaction point. The Monte Carlo simulation , - F, (a) o 4 / '~ ~. / i / o 0 _ L - "  I ~,. <1.0 2.6 5.0 3 .4  3.8 4.2 4.6 ~ 1  [ I I I I I J (e~,/z/2) (b) M,,, +~ _ d 4 o 0 F ' ~ l  p I 7 9 II 13 15 17 M~+{- (GeV) Fig. 1. Invariant mass spectra of e+e - ,  u+u- lepton pairs: (a) in the range 2.6-4.6 GeV, (b) in the range 6-18 GeV. The shaded events correspond to the expected invariant mass distribution from a Monte Carlo calculation with 5 quark flavors. The dotted curve of the ~ signal expected from the "non-perturbative model". 142 Volume 129, number 1,2 PHYSICS LETTERS 15 September 1983 does not include ff production,  and yields no £+£- event in the ~ region. The ff detect ion efficiency ranges between 1.5% and 2.1% depending on which model of  product ion is assumed (including the leptonic branching ratio of  14%). The less favorable mechanism is the "non-per- turbative model"  of  ref. [3]. Using the value of  1.5%, the corresponding 90% CL upper limit is: o(e+e - ~ C X )  < 4.4 X 10 36 cm 2 . Note that this upper limit corresponds to 4.3 X 10 - 2  o,w. This limit is a factor of  10 -100  above the values calculated in perturbative QCD models [2], but  it ex- cludes the large cross section expected from the non- perturbative model  of  Kane et al. [3] which would yield ~15 events in the plot  of  fig. I in the region 2 .5 -3 .3  GeV. Previous measurements were made of  inclusive f production in e+e - at x/)- = 4 . 0 - 5 . 0  GeV [71. We used similar methods to search for "I' produc- tion. There are no e+e - and/2+/1 - combinations with an invariant mass compatible with an "9 (9.4) mass. To estimate the detect ion efficiency we employed a per- turbative QCD matrix element based on the process e+e - -+ qf'gg and simulated events by Monte Carlo method.  We find eT = 1.4%. The corresponding 90% CL upper limit is a(e+e - -+ 'I 'X) < 4.7 X 10 -36  cm 2, or 4.6 X 10 -2  out. Our data may also be used to set an upper lilnit on the branching ratio BR(b -+ fiX) o f b  quarks into ff's and on the flavor-changing neutral current process b -+ £+£ X. We use the conventional model of  the B meson, assuming that the decay is controlled by the decay of  the b quark, the other quark (u, d, or s) hav- ing a spectator role. The efficiency to detect  ff ~ £+£- from B meson decay is 2.5%. The total number of  bb events is computed to be 10% of  the 9411 selected hadronic events. This leads to a 90% CL upper limit of: BR(b -+ fiX) < 4 .9%,  in agreement with the limit of  1.4% measured by the CLEO collaboration [8] at CESR. A simple theoreti- cal calculation [1] predicts a value of  BR(b ~ ~bX)/ BR(b -* all) -~ 3 -5%.  In the case of  the decay b ~ £+£-X, the invariant mass of  the leptons is expected to be rather large (fig. 2). A cut is therefore applied at M~+~- > 1.6 GeV. I I I I I I I 1 30 MONTE CARLO ,5 .~Jo z 8 0.4 1.2 2.0 2.8 5.6 4.4 5.2 M~. ~- (GeV) Fig. 2. Invariant massM£+£- distribution: the solid curve corresponds to a Monte Carlo calculation with 5 quark flavors, the dotted curve corresponds to decay B ~ £+£-X assuming that 10% of B mesons present in the data sample undergo this decay mode. Only pairs of  leptons in the same hemisphere are con- sidered with no cut in the lepton transverse momenta.  One candidate is left in the data, and 2 events are ex- pected from the background Monte Carlo calculation described previously. The acceptance for this neutral current decay mode is found by the Monte Carlo methods to be 13%, which leads to BR(b ~ £+£-X) < 0.8% at 90% CL.  Mong with similar limits obtained by MARK J at PETRA [9] and by CLEO at CESR [10], this result supports the assignment of  the b quark to a weak iso- doublet ,  implying therefore the existence of  a t quark [11]. In summary, we have searched for inclusive produc- tion of  J / ¢  (3.1) and T (9.4) via their decay into two leptons. No signals are observed. At 90% CL, we deter- mine o(e+e - -+ ~X) < 4.3 X 10 - 2  ou~ and o(e+e - "£X) < 4.6 × 10 - 2  ou~. The same data yield limits on the branching ratios for the b quark BR(b ~ ~OX) < 4.9% and BR(b ~ £+£-X) < 0.8%. References [l] H. Fritzch, Phys. Lett. B86 (1979) 164. 143 Volume 129, number 1,2 PHYSICS LETTERS 15 September 1983 [2] E.L. Berger and D. Jones, Phys. Rev. D23 (1981) 1521; G.C. Branco et al., Phys. Lett. 85B (1979) 269; H. Fritsch and J.H. Ktihn, Phys. Lett. B90 (1980) 164; J.H. Kiihn and tt. Schneider, Z. Phys. C11 (1981) 263; W. Keung, Phys. Rev. D23 (1981) 2072; L. Clavelli, ANL-HEP-PR-82-81. [3] G.L. Kane et al., Phys. Lett. 85B (1979) 115. [4] R.H. Schindler et al., Phys. Rev. D24 (1981) 78. [5] M. Nelson et al., submitted to Phys. Rev. Lett. [61 G. Hanson et al., Phys. Rev. Lett. 35 (1975) 1609. [7] J. Burmester et al., Phys. Lett. 68B (1977) 283. [8] B. Gittelman, CLNS-82/549. [9] A. B6hm, DESY 82-084. [10] CLEO Collab., Commun. XXI Intern. Conf. on High energy Physics (Paris, July 1982). [11] V. Barger and S. Pakvasa, Phys. Lett. 81B (1979) 195; G.L. Kane and M.E. Peskin, Nucl. Phys. B195 (1982) 29. 144 

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LIMITS ON J/PSI-PRODUCTION AND UPSILON-PRODUCTION IN E+E-INTERACTIONS AT SQUARE-ROOT-S=29 GEV

LIMITS ON J/PSI-PRODUCTION AND UPSILON-PRODUCTION IN E+E-INTERACTIONS AT SQUARE-ROOT-S=29 GEV

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