498 research outputs found
A Review of the Mass Measurement Techniques proposed for the Large Hadron Collider
We review the methods which have been proposed for measuring masses of new
particles at the Large Hadron Collider paying particular attention to the
kinematical techniques suitable for extracting mass information when invisible
particles are expected.Comment: 72 pages - in form to be published in JPhys
Precision Determination of Invisible-Particle Masses at the CERN LHC: II
We further develop the constrained mass variable techniques to determine the
mass scale of invisible particles pair-produced at hadron colliders. We
introduce the constrained mass variable M_3C which provides an event-by-event
lower bound and upper bound to the mass scale given the two mass differences
between the lightest three new particle states. This variable is most
appropriate for short symmetric cascade decays involving two-body decays and
on-shell intermediate states which end in standard-model particles and two
dark-matter particles. An important feature of the constrained mass variables
is that they do not rely simply on the position of the end point but use the
additional information contained in events which lie far from the end point. To
demonstrate our method we study the supersymmetric model SPS 1a. We select cuts
to study events with two Neutralino_2 each of which decays to Neutralino_1, and
two opposite-sign same-flavor (OSSF) charged leptons through an intermediate
on-shell slepton. We find that with 300 fb^-1 of integrated luminosity the
invisible-particle mass can be measured to M=96.4 +/- 2.4 GeV. Combining fits
to the shape of the M_3C constrained mass variable distribution with the max
m_ll edge fixes the mass differences to +/- 0.2 GeV.Comment: 13 pages, 10 figure
Re-weighing the evidence for a Higgs boson in dileptonic W-boson decays
We reconsider observables for discovering and measuring the mass of a Higgs
boson via its di-leptonic decays: H --> WW* --> l nu l nu. We define an
observable generalizing the transverse mass that takes into account the fact
that one of the intermediate W-bosons is likely to be on-shell. We compare this
new variable with existing ones and argue that it gives a significant
improvement for discovery in the region m_h < 2 m_W.Comment: 3 pages, 2 figures. Changes in v2: (i) implemented a model of
detector smearing, (ii) switched LHC simulation from 14 TeV to 7 TeV running,
(iii) presenting results for 10 rather than 3 inverse femtobarns, (iv)
corrected a typo in Fig 2 legend. Changes in v3: included published erratu
The Precision Determination of Invisible-Particle Masses at the LHC
We develop techniques to determine the mass scale of invisible particles
pair-produced at hadron colliders. We employ the constrained mass variable
m_2C, which provides an event-by-event lower-bound to the mass scale given a
mass difference. We complement this variable with a new variable m_2C,UB which
provides an additional upper bound to the mass scale, and demonstrate its
utility with a realistic case study of a supersymmetry model. These variables
together effectively quantify the `kink' in the function Max m_T2 which has
been proposed as a mass-determination technique for collider-produced dark
matter. An important advantage of the m_2C method is that it does not rely
simply on the position at the endpoint, but it uses the additional information
contained in events which lie far from the endpoint. We found the mass by
comparing the HERWIG generated m_2C distribution to ideal distributions for
different masses. We find that for the case studied, with 100 fb^-1 of
integrated luminosity (about 400 signal events), the invisible particle's mass
can be measured to a precision of 4.1 GeV. We conclude that this technique's
precision and accuracy is as good as, if not better than, the best known
techniques for invisible-particle mass-determination at hadron colliders.Comment: 20 pages, 11 figures, minor correction
The race for supersymmetry: using mT2 for discovery
We describe how one may employ a very simple event selection, using only the
kinematic variable mT2, to search for new particles at the LHC. The method is
useful when searching for evidence of models (such as R-parity conserving
supersymmetry) which have a Z2 parity and a weakly-interacting lightest
parity-odd particle. We discuss the kinematic properties which make this
variable an excellent discriminant against the great majority of Standard Model
backgrounds. Monte Carlo simulations suggest that this approach could be used
to discover supersymmetry with somewhat smaller integrated luminosities (or
perhaps lower center-of-mass energies) than would be required for other
comparable analyses.Comment: 8 page
Finding Higgs bosons heavier than 2 m_W in dileptonic W-boson decays
We reconsider observables for discovering a heavy Higgs boson (with m_h >
2m_W) via its di-leptonic decays h -> WW -> l nu l nu. We show that observables
generalizing the transverse mass that take into account the fact that both of
the intermediate W bosons are likely to be on-shell give a significant
improvement over the variables used in existing searches. We also comment on
the application of these observables to other decays which proceed via
narrow-width intermediates.Comment: v1:4 pages, 1 figure; v2: 6 pages, 2 figures, substantially revise
Detection of quantitative trait loci for locomotion and osteochondrosis-related traits in Large White x Meishan pigs.
Di-Higgs final states augMT2ed ā Selecting hh events at the high luminosity LHC
Higgs boson self-interactions can be investigated via di-Higgs (ppāhh+X) production at the LHC. With a small O(30) fb Standard Model production cross section, and a large View the MathML source background, this measurement has been considered challenging, even at a luminosity-upgraded LHC. We demonstrate that by using simple kinematic bounding variables, of the sort already employed in existing LHC searches, the dominant View the MathML source background can be largely eliminated. Simulations of the signal and the dominant background demonstrate the prospect for measurement of the di-Higgs production cross section at the 30% level using 3 abā1 of integrated luminosity at a high luminosity LHC. This corresponds to a Higgs self-coupling determination with 60% accuracy in the View the MathML source mode, with potential for further improvements from e.g. subjet technologies and from additional di-Higgs decay channels
A Storm in a "T" Cup
We revisit the process of transversification and agglomeration of particle
momenta that are often performed in analyses at hadron colliders, and show that
many of the existing mass-measurement variables proposed for hadron colliders
are far more closely related to each other than is widely appreciated, and
indeed can all be viewed as a common mass bound specialized for a variety of
purposes.Comment: 3 pages, 2 figures, presented by K.C. Kong at the 19th Particles and
Nuclei International Conference, PANIC 2011, MIT, Cambridge, MA (July 24-29,
2011
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