980 research outputs found
Finite top quark mass effects in NNLO Higgs boson production at LHC
We present next-to-next-to-leading order corrections to the inclusive
production of the Higgs bosons at the CERN Large Hadron Collider (LHC)
including finite top quark mass effects. Expanding our analytic results for the
partonic cross section around the soft limit we find agreement with a very
recent publication by Harlander and Ozeren \cite{Harlander:2009mq}.Comment: 15 page
The Impact of Measurements at Intermediate Energies on the Parameters of the Standard Model
We discuss the impact of precision measurements of in the center-of-mass range between 3 and 12 GeV, including
improvements in the electronic widths of the narrow charmonium and bottonium
resonances, on the determination of parameters of the Standard Model. In
particular we discuss the impact of potential improvements on the extraction of
the strong coupling constant , on the evaluation of the hadronic
contributions to the electromagnetic coupling , and the
determination of the charm and bottom quark masses.Comment: 8 page
Observation of Quasibound States of the Neutron in Matter
Quasistationary states of ultracold neutrons have been observed in a double-hump potential barrier. This potential barrier was created by sandwiching a thin film of aluminum between two thin copper films. Measurements of reflection from and transmission through such composite films displayed clear resonances. The resonance positions and widths are in agreement with calculations
ACCESS - V. Dissecting ram-pressure stripping through integral-field spectroscopy and multi-band imaging
We study the case of a bright (L>L*) barred spiral galaxy from the rich
cluster A3558 in the Shapley supercluster core (z=0.05) undergoing ram-pressure
stripping. Integral-field spectroscopy, complemented by multi-band imaging,
allows us to reveal the impact of ram pressure on the interstellar medium. We
study in detail the kinematics and the physical conditions of the ionized gas
and the properties of the stellar populations. We observe one-sided extraplanar
ionized gas along the full extent of the galaxy disc. Narrow-band Halpha
imaging resolves this outflow into a complex of knots and filaments. The gas
velocity field is complex with the extraplanar gas showing signature of
rotation. In all parts of the galaxy, we find a significant contribution from
shock excitation, as well as emission powered by star formation. Shock-ionized
gas is associated with the turbulent gas outflow and highly attenuated by dust.
All these findings cover the whole phenomenology of early-stage ram-pressure
stripping. Intense, highly obscured star formation is taking place in the
nucleus, probably related to the bar, and in a region 12 kpc South-West from
the centre. In the SW region we identify a starburst characterized by a 5x
increase in the star-formation rate over the last ~100 Myr, possibly related to
the compression of the interstellar gas by the ram pressure. The scenario
suggested by the observations is supported and refined by ad hoc
N-body/hydrodynamical simulations which identify a rather narrow temporal range
for the onset of ram-pressure stripping around t~60 Myr ago, and an angle
between the galaxy rotation axis and the intra-cluster medium wind of ~45 deg.
Taking into account that the galaxy is found ~1 Mpc from the cluster centre in
a relatively low-density region, this study shows that ram-pressure stripping
still acts efficiently on massive galaxies well outside the cluster cores.Comment: 46 pages, 21 figures, accepted for publication; MNRAS 201
Supersymmetric Higgs production in gluon fusion at next-to-leading order
The next-to-leading order (NLO) QCD corrections to the production and decay
rate of a Higgs boson are computed within the framework of the Minimal
Supersymmetric Standard Model (MSSM). The calculation is based on an effective
theory for light and intermediate mass Higgs bosons. We provide a Fortran
routine for the numerical evaluation of the coefficient function. For most of
the MSSM parameter space, the relative size of the NLO corrections is typically
of the order of 5% smaller than the Standard Model value. We exemplify the
numerical results for two scenarios: the benchmark point SPS1a, and a parameter
region where the gluon-Higgs coupling at leading order is very small due to a
cancellation of the squark and quark contributions.Comment: 27 pages, LaTeX, 31 embedded PostScript-files; v2: typos corrected,
reformatted in JHEP style; accepted for publication in JHE
Chromatin-contact atlas reveals disorder-mediated protein interactions and moonlighting chromatin-associated RBPs
RNA-binding proteins (RBPs) play diverse roles in regulating co-transcriptional RNA-processing and chromatin functions, but our knowledge of the repertoire of chromatin-associated RBPs (caRBPs) and their interactions with chromatin remains limited. Here, we developed SPACE (Silica Particle Assisted Chromatin Enrichment) to isolate global and regional chromatin components with high specificity and sensitivity, and SPACEmap to identify the chromatin-contact regions in proteins. Applied to mouse embryonic stem cells, SPACE identified 1459 chromatin-associated proteins, ∼48% of which are annotated as RBPs, indicating their dual roles in chromatin and RNA-binding. Additionally, SPACEmap stringently verified chromatin-binding of 403 RBPs and identified their chromatin-contact regions. Notably, SPACEmap showed that about 40% of the caRBPs bind chromatin by intrinsically disordered regions (IDRs). Studying SPACE and total proteome dynamics from mES cells grown in 2iL and serum medium indicates significant correlation (R = 0.62). One of the most dynamic caRBPs is Dazl, which we find co-localized with PRC2 at transcription start sites of genes that are distinct from Dazl mRNA binding. Dazl and other PRC2-colocalised caRBPs are rich in intrinsically disordered regions (IDRs), which could contribute to the formation and regulation of phase-separated PRC condensates. Together, our approach provides an unprecedented insight into IDR-mediated interactions and caRBPs with moonlighting functions in native chromatin
Effects of SUSY-QCD in hadronic Higgs production at next-to-next-to-leading order
An estimate of the NNLO supersymmetric QCD effects for Higgs production at
hadron colliders is given. Assuming an effective gluon-Higgs interaction, these
corrections enter only in terms of process-independent, factorizable terms. We
argue that the current knowledge of these terms up to NLO is sufficient to
derive the NNLO hadronic cross section within the limitations of the standard
theoretical uncertainties arising mainly from renormalization and factorization
scale variations. The SUSY contributions are small with respect to the QCD
effects, which means that the NNLO corrections to Higgs production are very
similar in the Standard Model and the MSSM.Comment: LaTeX, 5 pages, 3 embedded PostScript figure
The NNLO gluon fusion Higgs production cross-section with many heavy quarks
We consider extensions of the Standard Model with a number of additional
heavy quarks which couple to the Higgs boson via top-like Yukawa interactions.
We construct an effective theory valid for a Higgs boson mass which is lighter
than twice the lightest heavy quark mass and compute the corresponding Wilson
coefficient through NNLO. We present numerical results for the gluon fusion
cross-section at the Tevatron for an extension of the Standard Model with a
fourth generation of heavy quarks. The gluon fusion cross-section is enhanced
by a factor of roughly 9 with respect to the Standard Model value. Tevatron
experimental data can place stringent exclusion limits for the Higgs mass in
this model.Comment: 14 pages, 1 tabl
High-precision e-expansions of massive four-loop vacuum bubbles
In this paper we calculate at high-precision the expansions in e=(4-D)/2 of
the master integrals of 4-loop vacuum bubble diagrams with equal masses, using
a method based on the solution of systems of difference equations. We also show
that the analytical expression of a related on-shell 3-loop self-mass master
integral contains new transcendental constants made up of complete elliptic
integrals of first and second kind.Comment: 7 pages, 2 figures, LaTex, to be published in Physics Letters
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