616 research outputs found
Scaling in Complex Systems: Analytical Theory of Charged Pores
In this paper we find an analytical solution of the equilibrium ion
distribution for a toroidal model of a ionic channel, using the Perfect
Screening Theorem (PST). The ions are charged hard spheres, and are treated
using a variational Mean Spherical Approximation (VMSA) .
Understanding ion channels is still a very open problem, because of the many
exquisite tuning details of real life channels. It is clear that the electric
field plays a major role in the channel behaviour, and for that reason there
has been a lot of work on simple models that are able to provide workable
theories. Recently a number of interesting papers have appeared that discuss
models in which the effect of the geometry, excluded volume and non-linear
behaviour is considered.
We present here a 3D model of ionic channels which consists of a charged,
deformable torus with a circular or elliptical cross section, which can be flat
or vertical (close to a cylinder). Extensive comparisons to MC simulations were
performed.
The new solution opens new possibilities, such as studying flexible pores,
and water phase transformations inside the pores using an approach similar to
that used on flat crystal surfaces
CP violation Beyond the MSSM: Baryogenesis and Electric Dipole Moments
We study electroweak baryogenesis and electric dipole moments in the presence
of the two leading-order, non-renormalizable operators in the Higgs sector of
the MSSM. Significant qualitative and quantitative differences from MSSM
baryogenesis arise due to the presence of new CP-violating phases and to the
relaxation of constraints on the supersymmetric spectrum (in particular, both
stops can be light). We find: (1) spontaneous baryogenesis, driven by a change
in the phase of the Higgs vevs across the bubble wall, becomes possible; (2)
the top and stop CP-violating sources can become effective; (3) baryogenesis is
viable in larger parts of parameter space, alleviating the well-known
fine-tuning associated with MSSM baryogenesis. Nevertheless, electric dipole
moments should be measured if experimental sensitivities are improved by about
one order of magnitude.Comment: 33 pages, 6 figure
A Geometric Approach to CP Violation: Applications to the MCPMFV SUSY Model
We analyze the constraints imposed by experimental upper limits on electric
dipole moments (EDMs) within the Maximally CP- and Minimally Flavour-Violating
(MCPMFV) version of the MSSM. Since the MCPMFV scenario has 6 non-standard
CP-violating phases, in addition to the CP-odd QCD vacuum phase \theta_QCD,
cancellations may occur among the CP-violating contributions to the three
measured EDMs, those of the Thallium, neutron and Mercury, leaving open the
possibility of relatively large values of the other CP-violating observables.
We develop a novel geometric method that uses the small-phase approximation as
a starting point, takes the existing EDM constraints into account, and enables
us to find maximal values of other CP-violating observables, such as the EDMs
of the Deuteron and muon, the CP-violating asymmetry in b --> s \gamma decay,
and the B_s mixing phase. We apply this geometric method to provide upper
limits on these observables within specific benchmark supersymmetric scenarios,
including extensions that allow for a non-zero \theta_QCD.Comment: 34 pages, 16 eps figures, to appear in JHE
Precision Gauge Unification from Extra Yukawa Couplings
We investigate the impact of extra vector-like GUT multiplets on the
predicted value of the strong coupling. We find in particular that Yukawa
couplings between such extra multiplets and the MSSM Higgs doublets can resolve
the familiar two-loop discrepancy between the SUSY GUT prediction and the
measured value of alpha_3. Our analysis highlights the advantages of the
holomorphic scheme, where the perturbative running of gauge couplings is
saturated at one loop and further corrections are conveniently described in
terms of wavefunction renormalization factors. If the gauge couplings as well
as the extra Yukawas are of O(1) at the unification scale, the relevant
two-loop correction can be obtained analytically. However, the effect persists
also in the weakly-coupled domain, where possible non-perturbative corrections
at the GUT scale are under better control.Comment: 26 pages, LaTeX. v6: Important early reference adde
Cosmological evolution of the Higgs boson's vacuum expectation value
We point out that the expansion of the universe leads to a cosmological time evolution of the vacuum expectation of the Higgs boson. Within the standard model of particle physics, the cosmological time evolution of the vacuum expectation of the Higgs leads to a cosmological time evolution of the masses of the fermions and of the electroweak gauge bosons while the scale of Quantum Chromodynamics (QCD) remains constant. Precise measurements of the cosmological time evolution of u=me/mp, where me and mp are respectively the electron and proton mass (which is essentially determined by the QCD scale), therefore provide a test of the standard models of particle physics and of cosmology. This ratio can be measured using modern atomic clocks
Exploring the Higgs Portal with 10/fb at the LHC
We consider the impact of new exotic colored and/or charged matter
interacting through the Higgs portal on Standard Model Higgs boson searches at
the LHC. Such Higgs portal couplings can induce shifts in the effective
Higgs-gluon-gluon and Higgs-photon-photon couplings, thus modifying the Higgs
production and decay patterns. We consider two possible interpretations of the
current LHC Higgs searches based on ~ 5/fb of data at each detector: 1) a Higgs
boson in the mass range (124-126) GeV and 2) a `hidden' heavy Higgs boson which
is underproduced due to the suppression of its gluon fusion production cross
section. We first perform a model independent analysis of the allowed sizes of
such shifts in light of the current LHC data. As a class of possible candidates
for new physics which gives rise to such shifts, we investigate the effects of
new scalar multiplets charged under the Standard Model gauge symmetries. We
determine the scalar parameter space that is allowed by current LHC Higgs
searches, and compare with complementary LHC searches that are sensitive to the
direct production of colored scalar states.Comment: 27 pages, 11 figures; v2: references added, correction to scalar form
factor, numerical results updated with Moriond 2012 data, conclusions
unchange
Azimuthal Anisotropy of Photon and Charged Particle Emission in Pb+Pb Collisions at 158 A GeV/c
The azimuthal distributions of photons and charged particles with respect to
the event plane are investigated as a function of centrality in Pb + Pb
collisions at 158 A GeV/c in the WA98 experiment at the CERN SPS. The
anisotropy of the azimuthal distributions is characterized using a Fourier
analysis. For both the photon and charged particle distributions the first two
Fourier coefficients are observed to decrease with increasing centrality. The
observed anisotropies of the photon distributions compare well with the
expectations from the charged particle measurements for all centralities.Comment: 8 pages and 6 figures. The manuscript has undergone a major revision.
The unwanted correlations were enhanced in the random subdivision method used
in the earlier version. The present version uses the more established method
of division into subevents separated in rapidity to minimise short range
correlations. The observed results for charged particles are in agreement
with results from the other experiments. The observed anisotropy in photons
is explained using flow results of pions and the correlations arising due to
the decay of the neutral pion
Multiplicity Distributions and Charged-neutral Fluctuations
Results from the multiplicity distributions of inclusive photons and charged
particles, scaling of particle multiplicities, event-by-event multiplicity
fluctuations, and charged-neutral fluctuations in 158 GeV Pb+Pb
collisions are presented and discussed. A scaling of charged particle
multiplicity as and photons as have been observed, indicating violation of naive wounded nucleon model.
The analysis of localized charged-neutral fluctuation indicates a
model-independent demonstration of non-statistical fluctuations in both charged
particles and photons in limited azimuthal regions. However, no correlated
charged-neutral fluctuations are observed.Comment: Talk given at the International Symposium on Nuclear Physics
(ISNP-2000), Mumbai, India, 18-22 Dec 2000, Proceedings to be published in
Pramana, Journal of Physic
Azimuthal anisotropy and correlations at large transverse momenta in and Au+Au collisions at = 200 GeV
Results on high transverse momentum charged particle emission with respect to
the reaction plane are presented for Au+Au collisions at =
200 GeV. Two- and four-particle correlations results are presented as well as a
comparison of azimuthal correlations in Au+Au collisions to those in at
the same energy. Elliptic anisotropy, , is found to reach its maximum at
GeV/c, then decrease slowly and remain significant up to
-- 10 GeV/c. Stronger suppression is found in the back-to-back
high- particle correlations for particles emitted out-of-plane compared to
those emitted in-plane. The centrality dependence of at intermediate
is compared to simple models based on jet quenching.Comment: 4 figures. Published version as PRL 93, 252301 (2004
Azimuthal anisotropy in Au+Au collisions at sqrtsNN = 200 GeV
The results from the STAR Collaboration on directed flow (v_1), elliptic flow
(v_2), and the fourth harmonic (v_4) in the anisotropic azimuthal distribution
of particles from Au+Au collisions at sqrtsNN = 200 GeV are summarized and
compared with results from other experiments and theoretical models. Results
for identified particles are presented and fit with a Blast Wave model.
Different anisotropic flow analysis methods are compared and nonflow effects
are extracted from the data. For v_2, scaling with the number of constituent
quarks and parton coalescence is discussed. For v_4, scaling with v_2^2 and
quark coalescence is discussed.Comment: 26 pages. As accepted by Phys. Rev. C. Text rearranged, figures
modified, but data the same. However, in Fig. 35 the hydro calculations are
corrected in this version. The data tables are available at
http://www.star.bnl.gov/central/publications/ by searching for "flow" and
then this pape
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