58 research outputs found
Graviton Signals in Central Production at the LHC
In this paper, we study central production, in the inclusive case, to look
for graviton signals in large extra dimensional model using dilepton and
diphoton channels. We carefully analyze signal and possible Standard Model
background processes and study the feasibility of such new physics searches in
a relatively clean environment as in central production where the proton
fragments are mostly emitted in the forward direction, and there is a clear
rapidity gap between them and the centrally produced system. Our analysis shows
that the LHC with 14 TeV center of mass energy and 100 fb (300
fb) of integrated luminosity can probe the effective gravity scale up to
3.6 TeV (4.4 TeV) in both the dilepton and diphoton channels.Comment: 25 pages, 15 figure
Single Productions of Colored Particles at the LHC: An Example with Scalar Leptoquarks
Current LHC searches for new colored particles generally focus on their pair
production channels and assume any single production to be negligible. We argue
that such an assumption may be unnecessary in some cases. Inclusion of model
dependent single productions in pair production searches (or vice versa) can
give us new information about model parameters or better exclusion limits.
Considering the example of the recent CMS search for first generation scalar
leptoquarks in the pair production channel, we illustrate how single
productions can be systematically included in the signal estimations and
demonstrate how it can affect the mass exclusion limits and give new bounds on
leptoquark-lepton-quark couplings. We also estimate the effect of the pair
production in the more recent CMS search for scalar leptoquarks in single
production channels.Comment: 11 pages, 6 figures, 2 tables. References added. Comments added on LQ
single production search by CMS. Journal versio
Probing Compositeness with the CMS & Data
Quark-lepton compositeness is a well-known beyond the Standard Model (SM)
scenario with heavy exotic particles like leptoquarks (LQs) and leptogluons
(LGs) etc. These particles can couple to leptons and jets simultaneously. In
this letter, we use the recent CMS scalar LQ search data in the and
channels to probe this scenario. We recast the data in terms of a color
octet partner of the SM electron (or a first generation spin-1/2 LG) that
couples to an electron and a gluon via a dimension five operator suppressed by
the quark-lepton compositeness scale (). By combining different
production processes of the color octet electron () at the LHC, we use the
CMS 8TeV data to obtain a simultaneous bound on and the mass of the
(). We also study the reach of the 13 TeV LHC to discover the
and interpret the required luminosity in terms of and
.Comment: 7 pages, 6 figures, 3 tables. Minor changes, typos fixed. Matches
with the published versio
The 750 GeV excess from photon-photon and quark-quark processes
The observed excess in the diphoton mass spectrum around 750 GeV at the 13
TeV LHC possibly indicates the presence of a photonphilic resonance. We show
that the excess can be explained by a scalar of the type involved in
Bekenstein's framework for varying electromagnetic coupling theories. The
scalar, in our model, couples dominantly to photons and is mainly produced by
the quark-quark fusion at the LHC. In addition, it can also be produced in
photon-photon fusion. Our model has only two free parameters, the mass of the
scalar and the scale of the new physics, which are fixed by the LHC excess to
750 GeV and 1.5 - 2 TeV, respectively. The scalar has a large three-body decay
to a fermion pair and a photon, which provides an interesting search channel
with a dilepton-photon resonance around 750 GeV.Comment: 4 pages, 2 figures, 4 tables. Presented at the 51st Rencontres de
Moriond, QCD and High Energy Interactions, La Thuile, 19-26 March 201
Constraining minimal anomaly free extensions of the Standard Model
We consider a class of minimal anomaly free extensions of the
Standard Model with three generations of right-handed neutrinos and a complex
scalar. Using electroweak precision constraints, new 13 TeV LHC data, and
considering theoretical limitations such as perturbativity, we show that it is
possible to constrain a wide class of models. By classifying these models with
a single parameter, , we can put a model independent upper bound on the
new gauge coupling . We find that the new dilepton data
puts strong bounds on the parameters, especially in the mass region
.Comment: 23 pages, 4 figures. Modified model parametrization, exclusion limits
with new dat
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