SEARCH FOR NARROW RESONANCES IN e+e- ANNIHILATION - IN THE MASS REGION 3.2 TO 5.9 GeV*

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1 SEARCH FOR NARROW RESONANCES IN e+e- ANNIHILATION - IN THE MASS REGION 32 TO 59 GeV* c, SLAC-PUB-1523 LBL January 1975 (T/E) A M Boyarski, M Breidenbach, F Bulos, G J Feldan, G E Fischer, D Fryberger, G Hanson, B Jean-Marie,? R R Larsen, V Luth, H L Lynch, D Lyon, C C Morehouse, J-M: Paterson, M L Perl, P Rapidis, B Richter, R F Schwitters, W Tanenbau, and F -Vannucci$ Stanford Linear Accelerator Center Stanford University, Stanford, California GS Abras, D Briggs, W Chinowsky, CE Friedberg, G Goldhaber, J A Kadyk, A Litke, B Lulu, F Pierre, f: B Sadoulet, GH Trilling, J S Whitaker, J Wiss, and J E Zipse Lawrence Berkeley Laboratory and Departent of Physics University of California, Berkeley, California ABSTRACT We have searched the ass region 32 to 59 GeV for evidence of ++ narrow resonances in e e - hadrons We find no evidence for any such resonances other than the $(3695) in this region with a sensitivity ranging fro about 12 to 45% of the integrated cross section of the q(3695) The ore stringent bounds apply to resonances of a few MeV width, while the looser bounds apply to resonances of up to 20 MeV width (Subitted to Phys Rev Letters ) * Work supported by the U S Atoic Energy Coission t Peranent address : Laboratoire de 1 Accelerateur Lineaire, Centre d*orsay de 1 Universitd de Paris, 91 Orsay, France $ Peranent address : Institut de Physique Nucleaire, Orsay, France * Peranent address : Centre d Etudes Nuclkaires de Saclay, Saclay, France

2 i 2- After the discovery of the $(3105), ly2 we began a systeatic search for - other narrow resonances in e+e- annihilation c, In the first run of this search, 3 which extended fro 360 to 371 GeV, the #(3695) was discovered The search has been continued and now covers the ass region 32 to 59 GeV No evidence for other narrow resonances has been found The search, perfored at the SLAC e+e- colliding bea facility SPEAR, used the SLAC-LBL solenoidal agnetic detector The properties of this de- tector have been described previously 4 Events fro the process e+e- - hadrons are identified in the detector by the observation of three or ore charged tracks or two charged tracks acoplanar with the incident beas by ore than 20 The detection efficiency for hadronic events varies fro about 50% to 70% over the energy range of the search The luinosity is deterined by the easureent of e+e- scattering at 20 rad Details of the deterina- tion of the detection efficiency, backgrounds, and other corrections to the ea- sureent of total hadronic cross sections are discussed elsewhere The ass resolution is deterined by the energy spread in the colliding beas which arises ainly fro quantu fluctuations in the synchrotron radia- tion eitted by the beas The resolution varies as the energy squared and ranges fro 20 to 69 MeV (fwh) as the center of ass energy (EC ) in- creases fro 32 to 59 GeV 6 The search was conducted by autoatically increasing the center-of-ass 5 energy (twice the bea energy) by 188 MeV every few inutes Data taken during each step were analyzed in real tie and the relative cross sections were coputed at the end of each step The data were also written on agnetic tape for later reanalysis After each fill of the rings, the starting energy was norally set to overlap the previous scan by a few steps A few ass regions

3 -3- were scanned ore than once & igure 1 shows the relative cross sections for e+e- -, hadrons in 188 MeV steps in Ec The +(3695) is clearly visible, but no other structure is evi- dent Multiple easureents at the sae energy step have been cobined, but the region around the $(3695) represents a single scan of average luinosity and tie span The average tie spent at each step was 27 inutes at an av- erage luinosity of 11 X c -2 set-l We have set upper liits on the integrated cross sections for the production of narrow resonances in this ass region The integrated cross section is defined 2 = a& / WC where o is the resonant cross section and is assued to be a Breit-Wigner line shape We quote liits in ters of 2 since it is the only resolution-independent paraeter we can easure if the resonance width is less than the ass resolu- tion It is also directly related to the partial decay width of the resonance into electron pairs, Fee If the resonance has spin one, r ee 2 Z = i-p where is the ass of the resonance and B is the branching ratio into hadrons The liits were set by hypothesizing the existence of resonances at each energy and coparing the expected to the observed yield using Poisson statis- tics We ade a conservative background subtraction of 16 nb for EC - < 5 50 GeVand 12nbforEc > 50 GeV for nonresonant hadron production The liits for radiatively corrected7 integrated cross sections at the 90% confidence level are given in Table I For coparison, the integrated cross

4 -4- section of the $(3695) is of order 5000 nb MeV Thus, the upper liits range - frog 12 to 45% of the integrated cross section of the $(3695), with sensitivity decreasing as the resonance width increases i We plan to continue to search for narrow resonances at higher asses FOOTNOTES AND REFERENCES 1 J -E Augustin -- et al, Phys Rev Letters 33, 1406 (1974) 2 J J Aubert -- et al, Phys Rev Letters 33, 1404 (1974) 3 G S Abras et al Phys Rev Letters 33, , (1974) 4 J -E Augustin et al, -- Stanford Linear Accelerator Center Report No, SLAC-PUB-1501 (1974), to be published 5 J -E Augustin et al, -- Stanford Linear Accelerator Center Report No SLAC-PUB-1520 (1975), to be published 6 The resolutions given are those arising fro quantu fluctuations in the synchrotron radiation eitted by the circulating beas This energy spread has a Gaussian distribution There can also be a contribution to the spread fro instabilities in high peak current beas By easuring the peak cross sections of the $(3105) and $(3695) as a function of circulating bea current we have deterined that for the currents used in this exper- ient the increased energy spread was less than 5OYc at 31 GeV and less than 25% at 37 GeV This effect is expected to decrease rapidly with in- creasing energy 7 D R Yennie, Cornell University Report No CLNS-291 (1974), to be published; Y S Tsai and D R Yennie, private counications 8 The largest fluctuation is centered at GeV, where 8 events were detected for 2 expected There is an independent reason for considering this

5 I -5- a fluctuation rather than a signal A narrow resonance with an integrated cross section of 1470 nb MeV located at 3795 GeV would yield a radiative -h tail of about 13 nb at 3800 GeV (see Ref 7) We have previously taken extensive data at 3800 GeV and these data cannot reasonably support the existence of a radiative tail of that size (see Ref 5) If this fluctuation is excluded, then the liit on a narrow resonance in the region 3720 to 4000 GeV changes fro 1470 to 850 nb MeV FIGURE CAPTION 1 Relative cross sections for e e- - hadrons