the Mark II detector at the SLAC e+e- storage ring SPEAR. We have used events from the center-of-mass energy region 3.52 to 6.7 GeV to determine that B(Tr + ...
SLAC-PUB-2820 LBL-13413 September 1981
T/E A STUDY OF THE DECAY -c-+ ~T-u~*
C. A. W. W. G. G. R. A. M. J. D. J. G. J.
A. Blocker: J, M. Dorfan, G. S. Abrams, M. S. Alam,? M. Breidenbach, D. L. Burke, Blondel, §A. M. Boyarski, M. W. Coles,f+ S. Cooper,J‘t C. Carithers, W. Chinowsky, J. Dorenbosch,f M. W. Eaton, E. Dieterle, J. B. Dillon, J. Feldman, M. E. B. Franklin, G. Gidal, G. Goldhaber, D. G. Hitlin,Sf Hanson, K. G. Hayes,+ T. Himel,* P. Jenni,? J. Hollebeek, W. R. Innes, J. A. Jaros, R, R. Larsen, D. Johnson, J. A. Kadyk, A. J. Lankford, V. Li;th, R. E. Millikan, M. E. Nelson, C. Y. Pang, Levi,t F. Patrick, M. L. Per-l, B. Richter, A. Roussarie, R. F. Schwitters,q R. H. Schindler,? L. Scharre, L. Siegrist, J. Strait, H. Taureg,? M. Tonutti,(IB E. N. Vella, R. A. Vidal, I. Videau,§ H. Trilling, M. Weiss and H. Zaccone.§§ Lawrence Berkeley Laboratory and Department of Physics University of California, Berkeley, CA. 94720 and Stanford Linear Accelerator Center Stanford University, Stanford, CA. 94305 ABSTRACT We present
ing
ratio
for
the Mark II have used to
6.7
a high the
at the
from
the
GeV to determine
From electron-muon that
We present
measurements
mass of dronic
the decay
mode of
in the
of
the
for
branch-
ring
with SPEAR.
region
We
3.52
= 0.117~0.004~0.018.
same data
the
the
obtained
energy
+ n-vT)
-t
of
storage
e-;,v,)
the mass and spin
based,
(Submitted * Work supported 76SF00515 and
B(Tr
+ n-~~)/B(r-
T neutrino
data
center-of-mass
events B(T-
SLAC e+e-
that
determined
measurement
T- +lTv - Tt using
decay
detector events
statistics
first
sample,
we have
= 0.66'0.03'0.11. of the time,
'c and the
on a ha-
T. to Physics
by the Department W-7405-ENG-48.
of
Letters
B)
Energy,
contracts
DE-AC03-
-2-
All
of
measured
the
properties
to date
are
the
T as a sequential
the
decay
weak axial
vector
measurement coupling
If
to the
hadronic
We present
here
via
from is
corresponds
a measurement
measurements the
of
T neutrino All
58,600 the based
aspects
measurement summarize
of the
here
Charged
particles
by the
16 layers
the
of
the
where second side tillation Next
the
reflects
drift
chambers
counters comes the
the
detector
having
solenoidal
GeV
present
T and the mass of
pertinent
to (3)
elsewhere.
over
85% of
the
constrained
spatial
coil
angle chambers.
to the (p in
inter-
GeV/c)
and the resolution.
48 time-of-flight
a 300 picosecond
analysis.
solid
drift
this We
to this
cylindrical
200 micron
magnet
to 6.7
We also
relevant
tracks
are
detector
3.52
(O.OOSp)' is @ = ,/(0.0145)2+ P first term is from multiple-scattering
term
T'S
luminosity
vertex the
the
ratio
Mark II
from
the
A
IT-V~ decay mode.
central, for
the
pairs.
discussed
detected
The momentum resolution action
branching
characteristics are
of
of the
r'~-
Mark II
e-;,vT) c21
test
The integrated
'I- +
have been fully
-f
current.
with
correct,
hadronic
vector
and mass of
on the
of
is
standard
energies
produced spin
hypothesis the
weak axial
at center-of-mass to
interpretation
an unambiguous
-f r-v- T ) based on data taken at the e+e- storage ring SPEAR. 21000 rib-l
have been
known parameters.
B(=-
of
that
-+ n-vr)/B(~-
and B(T-
ratio
the
this
proceeds
calculated
of this
T lepton
with
lepton.
current
can be explicitly
the
consistent
~-v~ (1)
T- +
of
out -
(TOF) -scintiming
providing
resolution. a uniform
field
of
liquid
4.1
kilogauss.
argon
The energy
shower
20% at
shower
100 MeV.
are eight
65% of the
lead-
solid
angle.
and the photon greater
than
Outside
the
of
layers
tubes.
of
95% above shower
iron
One end of
a lead-proportional
counters
separated
the
detector
chamber
endcap
counter. Charged
were not
pions
according
(3) were
not
than
according
the
to
2.1
GeV/c).
able
from
TOF system
700 MeV/c,
from
that
radiative
For momenta above 90%, and the than
4%.
the
particles
the
range
for
identifying
Bhabha events
electron
(relevant
the
pion
for
protons
particle
than
be distinguishmomenta below
threshold
as a pion
counters,
momenta less
with
$ and Kz decays.
700 MeV/c,
shower
and (4) were not for
(1)
(2) were not
TOF system
(relevant
an electron from
which
argon
the
all
The efficiency
misidentifying
iess
to
GeV/c),
a muon rejects
known pions
82% to
lead-liquid
according 1.3
as particles
to the muon system,
The requirement
approximately fication.
identified
to the
kaons
momenta less
electrons
were
muons according
electrons
is
from
consisting
with
coil
12%//m,
of proportional
instrumented
the
covering
ranges
the muon system
by layers
with
is
efficiency
500 MeV down to
is
counters
resolution
detection
is
Outside
for
muon identi-
pions
was measured
The probability was measured
with
of known
and gamma conversions. efficiency
misidentification
ranges probability
from
-4-
Events exactly
were
the
of
if
exactly
had a charged
charged
two charged
low multiplicities
reduces
they
oppositely
one other,
requirement of
selected
contamination
from
particle
of
hadronic
and The
(X).
particles
typical
pion
takes
T events
advantage
and dramatically To reduce
events,
back-
ground from events involving neutrals, particularly the decay any event having a photon T +- pv T -t IT-ITOVT s we rejected with energy above 100 MeV. Photons less than 36 cm from a charged
particle,
ignored
because
To minimize event the
measured
identified
is
angles
the
There criteria.
given
two charged
were
in Table
two produced satisfying the ability of the
particle,
particles
had the
of missing
a particle (4)
the
the of
from mis-
we accepted
only
events
The acoplanarity
20°, difference
in
satisfying
from
the were
The estimated
same criteria
two particles
that
beam direction,,
particles
The feed-down
charged
problems.
backgrounds
the
both
twice.
1.
the
is
were
azimuthal
particles.
in which
counted
the
than
2150 or+ Xi events
Events
as IT'S were
A$
module,
we required
events,
greater
- A$ where
180'
of
angle
argon
recognition
To reduce
and p-pair
acoplanarity
angle
pattern
10 cm, along
point.
Bhabha
liquid
contamination,
be within
beam crossing
with
potential
af
beam-gas
vertex
at the
events
more than events
IT-+ X-s events
except
Assuming
was independent to
with
are
with
same charge,
feed-down
identified
backgrounds
was measured as the
above
of
rrr+ XT events
that
the
prob-
the
charge
was twice (5)
-5-
the
number
of
calculated
from
the
interaction
of
Carlo
backgrounds
are
in
the
program.
with
from
were
of uncertainties
The net
of
number
of
in
in
the
the
calculated
The errors
program.
simulation
was
a vertex
beam direction,
backgrounds
a combination
1138+46z174(63
these
the models
detector
by the
T+ Xi events
was
events.
The number (NaX) is
the
simulation
and uncertainties Carlo
of Xz events
The other
point.
a Monte
Monte
number
15 and 25 cm, along
between
from
The beam gas background
T+ X+ events,
of
related
TX events
to the
after
background
branching
ratio
subtraction
(B,)
for
T- -+ TT-V~
bY i Li 7r ci 5 ‘CT
N TX =2B where
the
and the
first
second
The quantity duction is
sum (index sum (index
for other
T decays
decay
modes includes equation
creation
of
over
integrated mode j,
a ITX event via
decay
decay
the spurious
and ~~j is
Bj
the
was easily
efficiencies “photons!
the
sum over
Equation
T-v~,
Carlo
to rVT
The branching Since
II.
by a Monte
pro-
when one T decays
‘c- +
which
-r-pair
‘c.
luminosity,
mode j,
shown in Table
energies
decay modes of the corrected
the
to decay
the
center-of-mass
is over
is
in Br,
E 1) s were determined d necessary to correct
is
radiatively
detecting
assumed are
to the
j)
Li
ratio
ratios
quadratic
the
section,
the branching
and the
is
o T-r i
cross
efficiency
i)
c B. ~~ j J rj
solved
loss
by the
is
a
once the It
program, for
(1)
of pattern
was events
due
recog-
-6-
nition
program
energy
and electronic
in
events
charged
from
with
same topology
particles
and no real Bhabha
-t v+la,
After
a 3% correction all
photons,
giving
the
radiative 5% for
errors
muon-pion
(l),
the
have measured sample
events
having
of
events
5% for
agreed
radia-
within
l%,
efficiencies (6)
systematic
error
some of
the
ratio
B(T-
for
the
an electron
the
system,
and no other
particles.
photon
branching
ratios
are propagated
through
on B(T-+
is
~-v~)
errors,such +
ratio
muon identified were
to come from
Gev
T ) , we the same
We selected
by the
There
15%.
as the
from
-c- + 71-~T analysis.
charged
state
spurious
in
branching
an oppositely
estimated
initial
-t ~-v~)/B(1-
identified
subtraction,
separation,
the
systematic
the ~leptonic
(2)
background
5% for
uncertainties errors
St3 were
the
1% for
When these
used
rays.
real,
yielding
electron-pion
separation,
net
for
The average
6%.
15% for
are
system,
of which
of
and cosmic
events
measurement,
in the
luminosity,
the types
and 5% for
To reduce
data
Bhabha
corrections,
jFT BjE?rlj .
Eq.
of
p-pairs
namely
+ e+e*),
(two
-+ IT-VT) = 0.117f0.004f0.018.
luminosity
correction, in
(e+e"
was measured
TX events
= 0,0654 and j3;:Tr B.E J TJ B(c-
6% for
as the photons),
correction
EITIT = 0.154
The systematic
deposited
correction
events
three
an average
were
of real
This
noise.
the
(e+e-
tive
a combination
liquid
argon
by the muon 294 e+,,g events
charm production,
-7-
30+7 from
other This
production, The average
and 2fl
T decays, gives
a net
efficiency
for
from multiprong
signal
detecting
of
257f17:8
eu
events
hadronic e+$
events,
was 0.071,
giving B(T-
e";,v,)
+
The systematic
error
6% for
rature: to the
the
-r-pair
B(r-
-f
value
This
is
B(-c- +
spurious
0.973,
in
of
0.58
following
added
radiative
section,
-t e-;ev.c)
is
the
efficiency
5% for
subtraction, Assuming
correction.
equal
in quad-
corrections
3% for
background
(3)
to the
muon and 1%
that theoretical
(2)
we have B(=-
-f
e-ievT)
= 0.176+0.006+0.010
B(T-
+-
P--G&)
= 0.171+0.006f0.010
excellent
agreement
= 0.170f0.011
e-ievT)
Equations
NTis
the
identification,
the
photon
Combining
This
electron
JA-;~v$'B(~of
cross
3% for
= 0.030~0.002~0.004,
5% for
luminosity,
5% for
identification, the
comes from
production
calculation,
for
B(=+ -+ p+vuGr)
(2)
-t 71-VT)/B(T-
with
the
and B(Tand (4)
with
and with
measurements
PLUTO (0.51f0.17),
previous
the
(4)
average C7) of
+- ~l-
