Measurement of the branching ratios psi-prime ---> e+ e-, psi-prime ---> J/psi pi pi and psi-prime ---> J/psi eta Page: 1 of 8
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Measurement of the branching ratios p' -- e+c-, p' -- J/irbr and p' -- J/+ r/.
M. Andreotti2, S. Bagnasco3,7, W. Baldini2, D. Bettoni2, G. Borreani7, A. Buzzo3, R. Calabrese2, R. Cester7,
G. Cibinetto2, P. Dalpiaz2, G. Garzoglio', K. E. Gollwitzer', M. Graham5, M. Hu1, D. Joffe6, J. Kasper6, G. Lasio4,
M. Lo Vetere3, E. Luppi2, M. Macri3, M. Mandelkern4, F. Marchetto7, M. Marinelli3, E. Menichetti7, Z. Metreveli',
R. Mussa7, M. Negrini2, M. M. Obertino7, M. Pallavicini3, N. Pastrone7, C. Patrignani3, T. K. Pedlar6, S. Pordes',
E. Robutti3, W. Roethel64, J. L. Rosen6, P. Rumerio6, R. Rusack5, A. Santroni3, J. Schultz4, S. H. Seo5,
K. K. Seth6, G. Stancari', M. Stancari4, A. Tomaradze6, I. Uman6, T. Vidnovic III', S. Werkema' and P. Zweber6
(FNAL experiment E835)
'Fermi National Accelerator Laboratory, Batavia, Illinois 60510
2lstituto Nazionale di Fisica Nucleare and University of Ferrara, 44100 Ferrara, Italy
3lstituto Nazionale di Fisica Nucleare and University of Genova, 16146 Genova, Italy
' University of California at Irvine, Irvine, California 92697
5 University of Minnesota, Minneapolis, Minnesota 55455
6Northwestern University, Evanston, Illinois 60208
7lstituto Nazionale di Fisica Nucleare and University of Torino, 10125 Torino, Italy
(Dated: December 14, 2005)
We have measured several branching ratios for u' decay using the data collected by FNAL
E835 experiment during year 2000, obtaining B(u' - e+e--) = 0.0068 + 0.0001 + 0.0004,
B3(x' ->J/$r+7--) = 0.292 + 0.005 + 0.018, B(' -> J/ r0x) = 0.167 + 0.005 + 0.014 and
B('-> J/yq) = 0.028 + 0.002 + 0.002. We also present a measurement of the dipion mass distri-
bution in the decays u' -> J/uww.
PACS numbers: 13.75.Cs, 14.40.GxI. INTRODUCTION
Branching ratios of p' decay have been measured by
many experiments in e+c collisions. The branching ra-
tios to e+c and to J/p inclusive states have been mea-
sured also by the Fermilab experiments E760 [1] and E835
[2], which studied charmonium spectroscopy in pp anni-
hilation.
The strong p' decays to J/p proceed mainly through
the emission of soft gluons by the cc pair, with their
subsequent hadronization [3]. The low gluon momen-
tum makes this process nonperturbative. However some
features of the hadronic process p' -> J/pX can be pre-
dicted using conservation laws. A prediction based on
isospin conservation is that B(p' -> J/gn7r0r)/B(1 -
J/ u7r+7r-) z. While previous measurements have al-
ways yielded slightly larger values, further checks of this
ratio are needed. The multipole expansion of the gluon
field [4] has been used to predict a value in the range 0.10
- 0.14 for F(p' -> J/py)/F(p' -> J/g7r+7r-) [5, 6] and
the r7r invariant mass distribution [7, 8].
II. EXPERIMENTAL METHOD
E835 studies charmonium spectroscopy in pp annihi-
lation. All cc states can be directly formed with this
technique. Since the cross section for charmonium for-
mation is at best ~ 5 orders of magnitude smaller than
the total pp cross section, in order to improve the signal
to noise ratio the charmonium signal is extracted from
the hadronic background by detecting electromagneticfinal states.
p' decays are studied here by selecting events with a
high invariant mass c+e- pair in the final state, coming
from the reactions:
' c+
b' ->J/7r+7r- ->E e -+7 -,
' -> J/v@k7r0 - e+e4y,
p' -J J/p - e+e2-.
The number NA of events observed for p' decay to a
given final state A is given by:
NA .bkg + EA J G(E) - 'BW (E)- B(- ' -> A)dE)
(1)
where is the integrated luminosity, Obk the background
cross section, EA the overall detection efficiency for the
channel, 'BW the Breit-Wigner cross section for pp -> ',
G(E) the center of mass energy distribution and B('
A) the branching ratio for the decay p' -> A.
Measuring the ratio of branching ratios for two chan-
nels A and B on the same data sample, several factors in
(1) cancel, leading to:B(p' -> A)
B(p' -> B)EB NA - Nbkg,A
EA NB NbgB '(2)
where N - Nbg is the number of events after the sub-
traction of the background contribution. The reference
channel has been chosen to be the J/b inclusive decay
because it is the one for which the ratio (2) presents the
lowest systematics, as will be shown in Section VI.C
C
ClCl
C
0
0
J'C
N
-
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Andreotti, M.; Bagnasco, S.; Baldini, W.; Bettoni, D.; Borreani, G.; Buzzo, A. et al. Measurement of the branching ratios psi-prime ---> e+ e-, psi-prime ---> J/psi pi pi and psi-prime ---> J/psi eta, article, February 1, 2005; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc880757/m1/1/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.