1,848 research outputs found

### Observability of MSSM Higgs bosons decaying to sparticles at the LHC

The possibility is discussed to observe the sparticle decay modes of the
heavy MSSM Higgs bosons at the Large Hadron Collider. We focus on the heavy
neutral Higgses, and argue that their decay into neutralinos may access an
interesting region in the MSSM parameter space up to masses around 450 GeV for
low and intermediate values of tan beta. If neutralinos and sleptons are light
enough, this channel - leading to a four lepton final state topology - can
complement the reach of the SM channels.Comment: 5 pages, 7 figures, proceedings for the 36th Rencontres de Moriond,
QCD and High Energy Hadronic Interactions, Les Arcs, France, March 17 - 24,
200

### Testing Invisible Momentum Ansatze in Missing Energy Events at the LHC

We consider SUSY-like events with two decay chains, each terminating in an
invisible particle, whose true energy and momentum are not measured in the
detector. Nevertheless, a useful educated guess about the invisible momenta can
still be obtained by optimizing a suitable invariant mass function. We review
and contrast several proposals in the literature for such ansatze: four
versions of the M_T2-assisted on-shell reconstruction (MAOS), as well as
several variants of the on-shell constrained M_2 variables. We compare the
performance of these methods with regards to the mass determination of a new
particle resonance along the decay chain from the peak of the reconstructed
invariant mass distribution. For concreteness, we consider the event topology
of dilepton ttbar events and study each of the three possible subsystems, in
both a ttbar and a SUSY example. We find that the M_2 variables generally
provide sharper peaks and therefore better ansatze for the invisible momenta.
We show that the performance can be further improved by preselecting events
near the kinematic endpoint of the corresponding variable from which the
momentum ansatz originates.Comment: 38 pages, 15 figure

### Search for a light Higgs boson in SUSY cascades

This note presents the potential of the CMS experiment to discover a light supersymmetric Higgs boson (h0) produced at the end of a cascade of supersymmetric particles starting with the strong production of squarks and gluinos. Because of this production mechanism, the events can be efficiently triggered using inclusive SUSY triggers such as jet+MET and the dominant h0 -> b bbar decay mode of the Higgs boson can be exploited. The Higgs mass can be extracted from the reconstructed di-b-jet effective mass distribution. The present investigation for the so-called LM5 test point has been done for 1, 3 and 10 fb-1

### Improving the sensitivity of stop searches with on-shell constrained invariant mass variables

The search for light stops is of paramount importance, both in general as a
promising path to the discovery of beyond the standard model physics and more
specifically as a way of evaluating the success of the naturalness paradigm.
While the LHC experiments have ruled out much of the relevant parameter space,
there are "stop gaps", i.e., values of sparticle masses for which existing LHC
analyses have relatively little sensitivity to light stops. We point out that
techniques involving on-shell constrained M_2 variables can do much to enhance
sensitivity in this region and hence help close the stop gaps. We demonstrate
the use of these variables for several benchmark points and describe the effect
of realistic complications, such as detector effects and combinatorial
backgrounds, in order to provide a useful toolkit for light stop searches in
particular, and new physics searches at the LHC in general.Comment: 49 pages, 28 figures, revised version published in JHEP, references
adde

### On-shell constrained $M_2$ variables with applications to mass measurements and topology disambiguation

We consider a class of on-shell constrained mass variables that are 3+1
dimensional generalizations of the Cambridge $M_{T2}$ variable and that
automatically incorporate various assumptions about the underlying event
topology. The presence of additional on-shell constraints causes their
kinematic distributions to exhibit sharper endpoints than the usual $M_{T2}$
distribution. We study the mathematical properties of these new variables,
e.g., the uniqueness of the solution selected by the minimization over the
invisible particle 4-momenta. We then use this solution to reconstruct the
masses of various particles along the decay chain. We propose several tests for
validating the assumed event topology in missing energy events from new
physics. The tests are able to determine: 1) whether the decays in the event
are two-body or three-body, 2) if the decay is two-body, whether the
intermediate resonances in the two decay chains are the same, and 3) the exact
sequence in which the visible particles are emitted from each decay chain.Comment: 44pages, 17 figures. revised version, published in JHEP. Minor
addition: a paragraph discussing the effect on the background at the end of
section 5.

### OPTIMASS: A Package for the Minimization of Kinematic Mass Functions with Constraints

Reconstructed mass variables, such as $M_2$, $M_{2C}$, $M_T^\star$, and
$M_{T2}^W$, play an essential role in searches for new physics at hadron
colliders. The calculation of these variables generally involves constrained
minimization in a large parameter space, which is numerically challenging. We
provide a C++ code, OPTIMASS, which interfaces with the MINUIT library to
perform this constrained minimization using the Augmented Lagrangian Method.
The code can be applied to arbitrarily general event topologies and thus allows
the user to significantly extend the existing set of kinematic variables. We
describe this code and its physics motivation, and demonstrate its use in the
analysis of the fully leptonic decay of pair-produced top quarks using the
$M_2$ variables.Comment: 39 pages, 12 figures, (1) minor revision in section 3, (2) figure
added in section 4.3, (3) reference added and (4) matched with published
versio

### Detection of MSSM Higgs bosons from supersymmetric particle cascade decays at the LHC

In the context of the Minimal Supersymmetric extension of the Standard Model,
we study the production of Higgs bosons at the Large Hadron Collider via
cascade decays of scalar quarks and gluinos. We focus on the cascades involving
heavier charginos and neutralinos, which decay into the neutral $h,A,H$ and
charged $H^\pm$ bosons and lighter charginos and neutralinos, but we will also
discuss direct decays of third--generation squarks into their lighter partners
and Higgs bosons as well as top quark decays into $H^\pm$ bosons. We show that
the production rates of relatively light Higgs bosons, M_\Phi \lsim 250 GeV,
via these mechanisms can be rather large in some areas of the parameter space.
Performing a fast detector simulation analysis that takes into account the
signals and the various backgrounds, we show that the detection of the neutral
Higgs bosons through their decays into $b\bar{b}$ pairs, and of the charged
Higgs particles through the $\tau^\pm \nu$ signature, is possible at the LHC.Comment: 44 pages, latex, 17 figure

### Discovery potential of top-partners in a realistic composite Higgs model with early LHC data

Composite Higgs models provide a natural, non-supersymmetric solution to the
hierarchy problem. In these models, one or more sets of heavy top-partners are
typically introduced. Some of these new quarks can be relatively light, with a
mass of a few hundred GeV, and could be observed with the early LHC collision
data expected to be collected during 2010. We analyse in detail the collider
signatures that these new quarks can produce. We show that final states with
two (same-sign) or three leptons are the most promising discovery channels.
They can yield a 5 sigma excess over the Standard Model expectation already
with the 2010 LHC collision data. Exotic quarks of charge 5/3 are a distinctive
feature of this model. We present a new method to reconstruct their masses from
their leptonic decay without relying on jets in the final state.Comment: 28 pages 11 Figures 7 Tables, minor changes, added references,
matches published versio

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