Research Article
Method of Studying Λ
0
Decays with One Missing Particle
Sheldon Stone and Liming Zhang
Physics Department, Syracuse University, Syracuse, NY 13244-1130, USA
Correspondence should be addressed to Sheldon Stone; stone@physics.syr.edu
Received March ; Revised July ; Accepted July ; Published September
Academic Editor: Alexey A. Petrov
Copyright © S. Stone and L. Zhang. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited. e publication of this article was funded by SCOAP
.
A new technique is discussed that can be applied to Λ
0
𝑏
baryon decays where decays with one missing particle can be discerned
from background and their branching fractions determined, along with other properties of the decays. Applications include
measurements of the CKM elements |
𝑢𝑏
|and |
𝑐𝑏
|and detection of any exotic objects coupling to →decays, such as the
inaton. Potential use of
0∗∗
→
+
−
and
0∗∗
𝑠
→
+
−
to investigate
−
decays is also commented upon.
1. Introduction
Detection of -avored hadron decays with one missing
neutral particle, such as a neutrino, is important for many
measurements and searches. ese include semileptonic
decays, such as
→
−
], →
−
],andanyexoticlong
livedparticlesthatcouldbeproducedindecayssuchas
→
,wherethe is any combination of detected particles
and the escapes the detector. (In this paper mention of
a particular decay mode implies the use of the charge-
conjugated mode as well.) ese measurements are possible
at an
+
−
collider operating at the Υ(4).SinceΥ(4) → ,
fully reconstructing either the or the
determines the
negative of the initial four-momentum of the other. With this
information it is possible to measure nal states where one
particle is not detected, such as a neutrino. To implement this
procedure, taking the
to be fully reconstructed, the missing
mass-squared,
2
𝑥
, is calculated including the information on
the initial four-momentum and measurements of the found
particles as
2
𝑥
=
𝐵
−
𝑋
2
−
𝐵
−
𝑋
2
,
()
where and
indicate energy and three-momentum, respec-
tively. Peaks in
2
𝑥
would be indicative of single missing
particles in the decay.
A related example is charm semileptonic decays with a
missing neutrino. Determinations of branching fractions and
form-factors have been carried out in xed target experi-
ments, exploiting the measured direction of the charmed
hadron and assuming that the missing particle has zero
mass, which leads to a twofold ambiguity in the neutrino
momentum calculation []. If the charm decay particle is a
0
, extra constraints can be imposed on its decay requiring it
to be produced from a
∗+
in the decay
∗+
→
+
0
.is
leads to more constraints than unknowns and is quite useful
for rejecting backgrounds [, ].
Interesting decays of the Λ
0
𝑏
baryon also exist, but
investigations are not feasible in the Υ(4) energy region.
Potential studies include determination of the CKM matrix
element |
𝑐𝑏
|, whichcanbedoneusingΛ
0
𝑏
→Λ
+
𝑐
−
] decays,
and |
𝑢𝑏
|using the Λ
0
𝑏
→
−
] mode.
Neutral particles that have not yet been seen could be
searched for, even if they are stable or have long enough
lifetimes that they would have only a very small fraction
of their decays inside the detection apparatus. One example
of such a possibly long-lived particle is the “inaton.” is
particle couples to a scalar eld and is responsible for
cosmological inaton. Bezrukov and Gorbunov predicted
branching fractions and decay modes of inatons, ,in
meson decays [] using a specic model, which is a particular
version of the simple chaotic ination with a quartic potential
Hindawi Publishing Corporation
Advances in High Energy Physics
Volume 2014, Article ID 931257, 5 pages
http://dx.doi.org/10.1155/2014/931257
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