4,699 research outputs found
Higgs boson production through annihilation at threshold in NLO QCD
We present threshold enhanced NLO QCD corrections to inclusive Higgs
production through bottom anti-bottom annihilation at hadron colliders using
threshold resummed cross section. The resummed cross section is obtained using
factorization properties and Sudakov resummation of the inclusive cross
section. We use the recent results on threshold NLO corrections in QCD for
Drell-Yan production and three loop QCD corrections to Higgs form factor with
bottom anti-bottom quark to achieve this task. This is the first step towards
the evaluation of complete NLO result. We have numerically demonstrated the
importance of such corrections at the LHC.Comment: 15 pages, 1 figur
Two-Loop QCD Corrections to Higgs Amplitude
Exclusive observables involving Higgs boson in association with jets are
often well suited to study the Higgs boson properties. They are rates involving
cuts on the final state jets or differential distributions of rapidity,
transverse momentum of the observed Higgs boson. While they get dominant
contributions from gluon initiated partonic subprocesses, it is important to
include the subdominant ones coming from other channels. In this article, we
study one such channel namely the Higgs production in association with a jet in
bottom anti-bottom annihilation process. We compute relevant amplitude
up to two loop level in QCD where Higgs couples
to bottom quark through Yukawa coupling. We use projection operators to obtain
the coefficients for each tensorial structure appearing in this process. We
have demonstrated that the renormalized amplitudes do have the right infrared
structure predicted by the QCD factorization in dimensional regularization. The
finite parts of the one and two loop amplitudes are presented after subtracting
the infrared poles using Catani's subtraction operators.Comment: Published version; 25 pages, 2 figures; v2: analytically continued
result added, typos are correcte
Spin-2 Form Factors at Three Loop in QCD
Spin-2 fields are often candidates in physics beyond the Standard Model
namely the models with extra-dimensions where spin-2 Kaluza-Klein gravitons
couple to the fields of the SM. Also, in the context of Higgs searches, spin-2
fields have been studied as an alternative to the scalar Higgs boson. In this
article, we present the complete three loop QCD radiative corrections to the
spin-2 quark-antiquark and spin-2 gluon-gluon form factors in SU(N) gauge
theory with light flavors. These form factors contribute to both
quark-antiquark and gluon-gluon initiated processes involving spin-2 particle
in the hadronic reactions at the LHC. We have studied the structure of infrared
singularities in these form factors up to three loop level using Sudakov
integro-differential equation and found that the anomalous dimensions
originating from soft and collinear regions of the loop integrals coincide with
those of the electroweak vector boson and Higgs form factors confirming the
universality of the infrared singularities in QCD amplitudes.Comment: 20 pages, 2 figure
Pseudo-scalar Higgs Boson Production at Threshold NLO and NLL QCD
We present the first results on the production of pseudo-scalar through gluon
fusion at the LHC to NLO in QCD taking into account only soft gluon
effects. We have used the effective Lagrangian that describes the coupling of
pseudo-scalar with the gluons in the large top quark mass limit. We have used
recently available quantities namely the three loop pseudo-scalar form factor
and the third order universal soft function in QCD to achieve this. Along with
the fixed order results, we also present the process dependent resummation
coefficient for threshold resummation to NLL in QCD. Phenomenological
impact of these threshold NLO corrections to pseudo-scalar production at
the LHC is presented and their role to reduce the renormalisation scale
dependence is demonstrated.Comment: 34 pages, 17 figure
Electrical transport across Au/Nb:SrTiO3 Schottky interface with different Nb doping
We have investigated electron transport in Nb doped SrTiO single crystals
for two doping densities. We find that the resistivity and mobility are
temperature dependent in both whereas the carrier concentration is almost
temperature invariant. We rationalize this using the hydrogenic theory for
shallow donors. Further, we probe electrical transport across Schottky
interfaces of Au on TiO terminated n-type SrTiO. Quantitative analysis
of macroscopic I-V measurements reveal thermionic emission dominated transport
for the low doped substrate whereas it deviates from such behavior for the high
doped substrate. This work is relevant for designing devices to study
electronic transport using oxide-semiconductors.Comment: 10 Pages, 3 Figure
A NuSTAR observation of the fast symbiotic nova V745 Sco in outburst
The fast recurrent nova V745 Sco was observed in the 3-79 keV X-rays band
with NuSTAR 10 days after the optical discovery. The measured X-ray emission is
consistent with a collisionally ionized optically thin plasma at temperature of
about 2.7 keV. A prominent iron line observed at 6.7 keV does not require
enhanced iron in the ejecta. We attribute the X-ray flux to shocked
circumstellar material. No X-ray emission was observed at energies above 20
keV, and the flux in the 3-20 keV range was about 1.6 10 erg
cm s. The emission measure indicates an average electron density
of order of 10 cm.
The X-ray flux in the 0.3-10 keV band almost simultaneously measured with
Swift was about 40 times larger, mainly due to the luminous central supersoft
source emitting at energy below 1 keV. The fact that the NuSTAR spectrum cannot
be fitted with a power law, and the lack of hard X-ray emission, allow us to
rule out Comptonized gamma rays, and to place an upper limit of the order of
10 erg cm s on the gamma-ray flux of the nova on the
tenth day of the outburst.Comment: in press in Monthly Notices of the Royal Astronomical Society, 201
Design of Linearly Polarized Rectangular Microstrip Patch Antenna Using IE3D/PSO
In this project, a novel particle swarm optimization method based on IE3D is used to design an Inset Feed Linearly Polarized Rectangular Microstrip Patch Antenna. The aim of the thesis is to Design and fabricate an inset fed rectangular Microstrip Antenna and study the effect of antenna dimensions Length (L) , Width (W) and substrate parameters relative Dielectric constant (εr) , substrate thickness on Radiation parameters of Band width. Low dielectric constant substrates are generally preferred for maximum radiation. The conducting patch can take any shape but rectangular and circular configurations are the most commonly used configuration. Other configurations are complex to analyze and require heavy numerical computations. The length of the antenna is nearly half wavelength in the dielectric; it is a very critical parameter, which governs the resonant frequency of the antenna. In view of design, selection of the patch width and length are the major parameters along with the feed line depth. Desired Patch antenna design is initially simulated by using IE3D simulator. And Patch antenna is realized as per design requirements
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