1,892 research outputs found

### Pseudo-Periodic Natural Higgs Inflation

Inflationary cosmology represents a well-studied framework to describe the
expansion of space in the early universe, as it explains the origin of the
large-scale structure of the cosmos and the isotropy of the cosmic microwave
background radiation. The recent detection of the Higgs boson renewed research
activities based on the assumption that the inflaton could be identified with
the Higgs field. At the same time, the question whether the inflationary
potential can be be extended to the electroweak scale and whether it should be
necessarily chosen ad hoc in order to be physically acceptable are at the
center of an intense debate. Here, we perform the slow-roll analysis of the
so-called Massive Natural Inflation (MNI) model which has three adjustable
parameters, the explicit mass term, a Fourier amplitude u, and a frequency
parameter $\beta$, in addition to a constant term of the potential. This theory
has the advantage to present a structure of infinite non-degenerate minima and
is amenable to an easy integration of high-energy modes. We show that, using
PLANCK data, one can fix, in the large $\beta$-region, the parameters of the
model in a unique way. We also demonstrate that the value for the parameters
chosen at the cosmological scale does not influence the results at the
electroweak scale. We argue that other models can have similar properties both
at cosmological and electroweak scales, but with the MNI model one can complete
the theory towards low energies and easily perform the integration of modes up
to the electroweak scale, producing the correct order-of-magnitude for the
Higgs mass.Comment: 12 pages, 6 figures, published in Nuclear Physics

### Ultra-High Energy Neutrino-Nucleon Scattering and Parton Distributions at Small $x$

The cross section for ultra-high energy neutrino-nucleon scattering is very
sensitive to the parton distributions at very small values of Bjorken x ($x
\leq 10^{-4})$. We numerically investigate the effects of modifying the
behavior of the gluon distribution function at very small $x$ in the DGLAP
evolution equation. We then use the Color Glass Condensate formalism to
calculate the neutrino-nucleon cross section at ultra-high energies and compare
the result with those based on modification of DGLAP evolution equation.Comment: 10 pages, 4 figures, INT-PUB-05-3

### Shadowing of gluons in perturbative QCD: A comparison of different models

We investigate the different perturbative QCD-based models for nuclear
shadowing of gluons. We show that in the kinematic region appropriate to RHIC
experiment, all models give similar estimates for the magnitude of gluon
shadowing. At scales relevant to LHC, there is a sizable difference between
predictions of the different models.Comment: 11 pages, 4 figure

### Differential susceptibility to fathers’ care and involvement: The moderating effect of infant reactivity

The differential susceptibility hypothesis suggests that children differ in their susceptibility to the influence of both positive and negative environmental factors. Children with reactive temperaments are hypothesised to be particularly susceptible to environmental influences, both for better and for worse. The present study sought to investigate whether infant temperament moderates the influence of fathers on child prosocial and problem behaviours. In a large prospective population study (Avon Longitudinal Study of Parents and Children), 5064 children were followed between the ages of six and 81 months (6¾ years). Infant temperament, child behaviours, and fathers’ involvement and depression were assessed

### Cronin Effect at Different Rapidities at RHIC

Calculations of the nuclear modification factor, R_dAu, for pi^0 production
in dAu collisions at s_NN^1/2 = 200 GeV are presented. The applied
pQCD-improved parton model incorporates intrinsic k_T. Nuclear multiscattering
and nuclear shadowing are considered in the Au nucleus. Theoretical results are
displayed for midrapidity and high pseudorapidity (eta), and compared to
preliminary PHENIX and BRAHMS data.Comment: Contributed to 17th International Conference on Ultra Relativistic
Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California, 11-17
Jan 200

### Forward Quark Jets from Protons Shattering the Colored Glass

We consider the single-inclusive minijet cross section in pA at forward
rapidity within the Color Glass Condensate model of high energy collisions. We
show that the nucleus appears black to the incident quarks except for very
large impact parameters. A markedly flatter p_t distribution as compared to QCD
in the dilute perturbative limit is predicted for transverse momenta about the
saturation scale, which could be as large as Q_s^2 ~ 10 GeV^2 for a gold
nucleus boosted to rapidity ~10 (as at the BNL-RHIC).Comment: 9 pages, no figure

### The initial energy density of gluons produced in very high energy nuclear collisions

In very high energy nuclear collisions, the initial energy of produced gluons
per unit area per unit rapidity, $dE/L^2/d\eta$, is equal to $f(g^2\mu L)
(g^2\mu)^3/g^2$, where $\mu^2$ is proportional to the gluon density per unit
area of the colliding nuclei. For an SU(2) gauge theory, we perform a
non--perturbative numerical computation of the function $f(g^2\mu L)$. It
decreases rapidly for small $g^2\mu L$ but varies only by $\sim 25$%, from
$0.208\pm 0.004$ to $0.257\pm 0.005$, for a wide range 35.36--296.98 in $g^2\mu
L$, including the range relevant for collisions at RHIC and LHC. Extrapolating
to SU(3), we estimate the initial energy per unit rapidity for Au-Au collisions
in the central region at RHIC and LHC.Comment: 11 pages, Latex, 3 figures; revised version-includes additional
numerical data; reference adde

### Non-linear evolution in CCFM: The interplay between coherence and saturation

We solve the CCFM equation numerically in the presence of a boundary
condition which effectively incorporates the non-linear dynamics. We retain the
full dependence of the unintegrated gluon distribution on the coherence scale,
and extract the saturation momentum. The resulting saturation scale is a
function of both rapidity and the coherence momentum. In Deep Inelastic
Scattering this will lead to a dependence of the saturation scale on the photon
virtuality in addition to the usual x-Bjorken dependence. At asymptotic
energies the interplay between the perturbative non-linear physics, and that of
the QCD coherence, leads to an interesting and novel dynamics where the
saturation momentum itself eventually saturates. We also investigate various
implementations of the "non-Sudakov" form factor. It is shown that the
non-linear dynamics leads to almost identical results for different form
factors. Finally, different choices of the scale of the running coupling are
analyzed and implications for the phenomenology are discussed.Comment: 37 pages, 21 figure

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