3,707 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
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
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
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
Pseudo-scalar Higgs boson production at NLO+NLL
We consider the production of a pseudo-scalar particle at the LHC, and
present accurate theoretical predictions for its inclusive cross section in
gluon fusion. The prediction is based on combining fixed-order perturbation
theory and all-order threshold resummation. At fixed order we include the exact
next-to-next-to-leading order (NNLO) plus an approximate
next-to-next-to-next-to-leading order (NLO) which is based on the
recent computation at this order for the scalar case. We then add threshold
resummation at next-to-next-to-next-to leading logarithmic accuracy
(NLL). Various forms of threshold resummation are considered,
differing by the treatment of subleading terms, allowing a robust estimate of
the theoretical uncertainties due to missing higher orders. With particular
attention to pseudo-scalar masses of GeV and GeV, we also observe
that perturbative convergence is much improved when resummation is included.
Additionally, results obtained with threshold resummation in direct QCD are
compared with analogous results as computed in soft-collinear effective theory,
which turn out to be in good agreement. We provide precise predictions for
pseudo-scalar inclusive cross section at TeV LHC for a wide range of
masses. The results are available through updated versions of the public codes
ggHiggs and TROLL.Comment: 14 pages, 7 figures, 1 table. Now includes a more precise assessment
of the uncertainty on the approximate N3LO. Final version accepted by EPJ
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