4,403 research outputs found
The Reconstruction of Trilinear Higgs Couplings
To establish the Higgs mechanism {\it sui generis} experimentally, the Higgs
self-interaction potential must be reconstructed. This task requires the
measurement of the trilinear and quadrilinear self-couplings, as predicted in
the Standard Model or in supersymmetric theories. The couplings can be probed
in multiple Higgs production at high-luminosity e+e- linear colliders. We
present the theoretical analysis for the production of neutral Higgs-boson
pairs in the relevant channels of double Higgs-strahlung and associated
multiple Higgs production.Comment: 20 pages, Proceedings, "Physics with a High-Luminosity e+e- Linear
Collider", DESY/ECFA LC Workshop, DESY 99-123
Production of Neutral Higgs-Boson Pairs at LHC
The reconstruction of the Higgs potential in the Standard Model or
supersymmetric theories demands the measurement of the trilinear Higgs
couplings. These couplings affect the multiple production of Higgs bosons at
high energy colliders. We present a systematic overview of the cross sections
for the production of pairs of (light) neutral Higgs bosons at the LHC. The
analysis is carried out for the Standard Model and its minimal supersymmetric
extension.Comment: Latex, 11 pages, uses feynmp.sty [included]. The complete paper,
including figures, is also available via anonymous ftp at
ftp://ttpux2.physik.uni-karlsruhe.de/ttp99/ttp99-17/ or via www at
http://www-ttp.physik.uni-karlsruhe.de/Preprints
Testing Higgs Self-couplings at e^+e^- Linear Colliders
To establish the Higgs mechanism sui generis experimentally, the self-energy
potential of the Higgs field must be reconstructed. This task requires the
measurement of the trilinear and quadrilinear self-couplings, as predicted, for
instance, in the Standard Model or in supersymmetric theories. The couplings
can be probed in multiple Higgs production at high-luminosity e^+e^- linear
colliders. Complementing earlier studies to develop a coherent picture of the
trilinear couplings, we have analyzed the production of pairs of neutral Higgs
bosons in all relevant channels of double Higgs-strahlung, associated multiple
Higgs production and WW/ZZ fusion to Higgs pairs.Comment: The complete paper, including figures, is also available via
anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ttp99/ttp99-02/ or via
www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/webmaster/preprints
Automation of NLO processes and decays and POWHEG matching in WHIZARD
We give a status report on the automation of next-to-leading order processes
within the Monte Carlo event generator WHIZARD, using GoSam and OpenLoops as
provider for one-loop matrix elements. To deal with divergences, WHIZARD uses
automated FKS subtraction, and the phase space for singular regions is
generated automatically. NLO examples for both scattering and decay processes
with a focus on e+e- processes are shown. Also, first NLO-studies of
observables for collisions of polarized leptons beams, e.g. at the ILC, will be
presented. Furthermore, the automatic matching of the fixed-order NLO
amplitudes with emissions from the parton shower within the POWHEG formalism
inside WHIZARD will be discussed. We also present results for top pairs at
threshold in lepton collisions, including matching between a resummed threshold
calculation and fixed-order NLO. This allows the investigation of more
exclusive differential observables.Comment: 5 pages, 3 figures, Talk presented at ACAT 2016 at UTFSM,
Valpara\'iso, Chil
The Abundance of Interstellar Nitrogen
Using the HST Goddard High Resolution Spectrograph (GHRS), we have obtained
high S/N echelle observations of the weak interstellar N I 1160, 1161 A
absorption doublet toward the stars Gamma Cas, Lambda Ori, Iota Ori, Kappa Ori,
Delta Sco, and Kappa Sco. In combination with a previous GHRS measurement of N
I toward Zeta Oph, these new observations yield a mean interstellar gas phase
nitrogen abundance (per 10 H atoms) of 10 N/H = 75 +/- 4. There are no
statistically significant variations in the measured N abundances from
sightline to sightline and no evidence of density-dependent depletion from the
gas-phase. Since N is not expected to be depleted much into dust grains in
these diffuse sightlines, its gas-phase abundance should reflect the total
interstellar abundance. Consequently, the GHRS observations imply that the
abundance of interstellar nitrogen (gas plus grains) in the local Milky Way is
about 80% of the solar system value of 10 N/H = 93 +/- 16. Although this
interstellar abundance deficit is somewhat less than that recently found for
oxygen and krypton with GHRS, the solar N abundance and the N I oscillator
strengths are too uncertain to definitively rule out either a solar ISM N
abundance or a 2/3 solar ISM N abundance similar to that of O and Kr.Comment: 14 pages, LaTeX, 2 Postscript figures; ApJ Letters, in pres
Top Physics in WHIZARD
In this talk we summarize the top physics setup in the event generator
WHIZARD with a main focus on lepton colliders. This includes full six-, eight-
and ten-fermion processes, factorized processes and spin correlations. For
lepton colliders, QCD NLO processes for top quark physics are available and
will be discussed. A special focus is on the top-quark pair threshold, where a
special implementation combines a non-relativistic effective field theory
calculation augmented by a next-to-leading threshold logarithm resummation with
a continuum relativistic fixed-order QCD NLO simulation.Comment: 6 pages, 2 figures, Talk presented at the International Workshop on
Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 201
Reparameterization Invariance to all Orders in Heavy Quark Effective Theory
Heavy Quark Effective Theory splits a heavy quark momentum into a large fixed
momentum and a variable residual momentum, p = m_Q v + k. It thereby suffers a
redundancy of description corresponding to small changes in the choice of the
fixed velocity, v. The fact that full QCD is manifestly v-independent should
lead to a non-trivial constraint on the form of the effective theory, known as
Reparameterization Invariance. For spin-1/2 quarks, the precise form of the
constraint and its solution at the level of the effective lagrangian have
proven to be rather subtle, and the original proposal by Luke and Manohar has
been questioned. In this paper I employ a version of Heavy Quark Effective
Theory containing the ``anti-particle'' field as a non-propagating auxiliary
field, which greatly simplifies keeping track of v-dependence. This permits a
very simple derivation of Reparameterization Invariance from first principles.
The auxiliary field can also be integrated out to return to the standard
formulation of the effective theory, but with the effective lagrangian now
satisfying the full reparameterization constraint. I compare this result with
earlier proposals.Comment: 12 pages, LaTex. Important and confusing typographical error in eq.
(15) corrected. To appear in Phys. Rev.
Correlation length in cuprates deduced from the impurity-induced magnetization
We report a new multi-nuclei based NMR method which allows us to image the
staggered polarization induced by nonmagnetic Li impurities in underdoped O6.6
and slightly overdoped O7 YBa2Cu3O6+y above T_C. The spatial extension of the
polarization xi_imp approximately follows a Curie law, increasing up to six
lattice constants at T=80K at O6.6 in the pseudogap regime. Near optimal
doping, the staggered magnetization has the same shape, with xi_imp reduced by
a factor 2. xi_imp is argued to reveal the intrinsic magnetic correlation
length of the pure system. It is found to display a smooth evolution through
the pseudogap regime.Comment: 8 latex pages + 8 figures, to appear in Physical Review B, this
resubmitted version is twice longer than the previous one : we detail here
our method to determine the impurity-induced magnetizatio
The reaction cross section
The one- and two-step mechanisms of the reaction in
the range of incident proton kinetic energy 1.13-3.0 GeV have been
investigated. A remarkable peculiarity of the two-step mechanism which
incorporates subprocesses and is the so
called velocity matching providing the presence of all intermediate particles
nearly to the on-mass-shell. The differential cross section has been calculated
using a realistic model for the hypertritium wave function. The
maximum value of the cross section is estimated as 1nb/sr. The
contribution of the one-step mechanism with the elementary process into the cross section has been found to be two - three orders of
magnitude smaller in comparison with the two-step mechanism.Comment: 10 pages, Latex, 3 Postscript figure
A quantum protocol for cheat-sensitive weak coin flipping
We present a quantum protocol for the task of weak coin flipping. We find
that, for one choice of parameters in the protocol, the maximum probability of
a dishonest party winning the coin flip if the other party is honest is
1/sqrt(2). We also show that if parties restrict themselves to strategies
wherein they cannot be caught cheating, their maximum probability of winning
can be even smaller. As such, the protocol offers additional security in the
form of cheat sensitivity.Comment: 4 pages RevTex. Differs from the journal version only in that the
sentences: "The ordering of the authors on this paper was chosen by a coin
flip implemented by a trusted third party. TR lost." have not been remove
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