CDF B spectroscopy results: B** and Bc{sup +} Page: 3 of 5
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CDF/PUB/BOTTOM/PUBLIC/5076
FERMILAB-Conf-99/227-E
CDF B spectroscopy results: B** and B
G. Bauer
(representing the CDF Collaboration)
Laboratory for Nuclear Science, Massachusetts Institute of Technology,
Cambridge, MA 02139 USA
E-mail: bauergefnal . gov
Abstract
We report on two spectroscopy results from CDF. First, we observe the orbitally
excited B** mesons in B - D(*)X events. We find 28 6 + 3% of light B
mesons produced are B** states. A collective mass fit results in a B1 mass of
5.71 0.02 GeV/c2. Secondly, we observe 20.4+6 decays of B+ -+ J/4t6+X, with
a 6.40 0.39 0.13 GeV/c2 mass and 0.46tit 0.03ps lifetime. The production
rate is in reasonable accordance with expectations.1. Introduction
The large b cross section at the Tevatron make it an
attractive arena for studying b-hadrons. CDF has
reported a variety of spectroscopy results, including
the most precise mass determinations of the B? [1]
and A? [2]. Here we report results on the rare B+
and the not rare, but hard to observe, B** states.
2. B** production
The B** states are the 4 orbitally (L = 1) excited
states of the B meson. In a relativistic light-quark
model the states B1, B2, Bo, and B* have masses
5.719, 5.733, 5.738, and 5.757 GeV/c2 [3]. Being
above the x-threshold, they decay via B** - B(*) r.
The normally broad (~100 MeV) hadronic decay
width is expected to be suppressed (~20 MeV) for
B1 and B* because only L = 2 decays are allowed.
Study of B**'s is of interest for non-perturbative
QCD models, and for "engineering" b-flavor tagging
methods [4,5]. B**'s have been observed in e+e-
collisions [6]. Here we report the first observation
of B**'s in a hadron collider.
We use 110 pb-1 of data collected in Run I. We
reconstruct 6 modes of the type B - D(*)LX [7],
all of which have been previously documented [5]
except for the addition of e+o, D0 -K+-7+--.
Side-band subtractions are performed, and we
effectively obtain a pure sample of almost 104 B's.
B**'s should be narrow peaks on a broad struc-
ture in the Br mass. Even after kinematic correc-
tions (~15%) the lost v, as well as the unidenti-
fied y from B* decay, smears these peaks. With
background, it is then extremely difficult to identifyB**'s. These problems are ameliorated by using the
quantity Q - m[tD(*)7] - m[LD(*)] - m[] which
compresses the broad m[LD(*)7] distribution (with
fD(*) ~ B) into a relatively narrow range at low Q.
We combine B's with tracks (PT > 0.9 GeV/c),
assumed to be x's, from the primary vertex (impact
parameter <-3a) to form B** candidates. These
B-7r combinations contain a variety of backgrounds
uncorrelated to the B: random x's from the under-
lying event and from multiple pp collisions. These
backgrounds may be removed by "sideband subtrac-
tion" methods. The major remaining background is
from pions from the hadronization of the B, which,
unfortunately, is correlated with the B, and thus
demands careful treatment.
B** decays give B+x- or BOx+ ("right-sign")
combinations at low-Q, and not B+7+ or B0x7
("wrong-sign"). The B-x Q-distributions, divided
into B+ and B0 mesons and into right/wrong-sign
categories, are shown in Fig. 1. The data (points)
show a clear right-sign excess, but B+ and B0
behave differently and the wrong-sign background
peaks in the same Q-region. The B** signal is
entangled with the hadronization background which
also favors the right-sign at low Q-values (the basis
for our "same side tagging" [4,5]). Thus, one can
not expose a B** signal by subtracting the "wrong-
sign" Q-distributions from the "right-sign" ones.
We model the hadronization Q-distributions by
2-parameter functions inspired by PYTHIA [8],
and impose the relative right/wrong-sign hadron-
ization asymmetry from the simulation. We fit the
data for B** signal plus this hadronization model.$
: Other small backgrounds, such as B**, are included. The
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Bauer, G. CDF B spectroscopy results: B** and Bc{sup +}, article, September 8, 1999; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc625111/m1/3/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.