449 research outputs found
Asymptotic Laws for Joint Content Replication and Delivery in Wireless Networks
We investigate on the scalability of multihop wireless communications, a
major concern in networking, for the case that users access content replicated
across the nodes. In contrast to the standard paradigm of randomly selected
communicating pairs, content replication is efficient for certain regimes of
file popularity, cache and network size. Our study begins with the detailed
joint content replication and delivery problem on a 2D square grid, a hard
combinatorial optimization. This is reduced to a simpler problem based on
replication density, whose performance is of the same order as the original.
Assuming a Zipf popularity law, and letting the size of content and network
both go to infinity, we identify the scaling laws and regimes of the required
link capacity, ranging from O(\sqrt{N}) down to O(1)
Resonance production by neutrinos: I. J=3/2 Resonances
The article contains general formulas for the production of J=3/2 resonances
by neutrinos and antineutrinos. It specializes to the P_{33}(1232) resonance
whose form factors are determined by theory and experiment and then are
compared with experimental results at low and high energies. It is shown that
the minimum in the low Q^2 region is a consequence of a combined effect from
the vanishing of the vector form factors, the muon mass and Pauli blocking.
Several improvements for the future investigations are suggested.Comment: 10 pages, LaTeX, misprints corrected, 1 reference adde
Modified Paschos-Wolfenstein relation and extraction of weak mixing angle sin^2 theta_W
The NuTeV collaboration reported anomalously large weak mixing angle sin^2
theta_W in comparison with the standard model prediction. Neutrino and
antineutrino charged- and neutral-current events are analyzed for extracting
sin^2 theta_W. Although the Paschos-Wolfenstein relation is not directly used
in the analysis, it plays an important role in the determination. Noting that
the target nucleus, iron, is not an isoscalar nucleus, we derive a
leading-order expression for a modified Paschos-Wolfenstein relation for
nuclei, which may have neutron excess. Then, using charge and baryon-number
conservations for nuclei, we discuss a nuclear correction in the sin^2 theta_W
determination. It is noteworthy that nuclear modifications are different
between valence up- and down-quark distributions. We show this difference
effect on the NuTeV sin^2 theta_W deviation.Comment: 5 pages, REVTeX4.0, revtex4.cls, url.sty, natbib.sty, revsymb.sty,
10pt.rtx, aps.rtx, amssymb.sty, amsfonts.sty, 3 eps figures. Phys. Rev. D in
press. Email: [email protected] See also http://hs.phys.saga-u.ac.j
Coherent pion production by neutrinos on nuclei
The main part of coherent pion production by neutrinos on nuclei is
essentially determined by PCAC, provided that the leptonic momentum transferred
square Q^2 remains sufficiently small. We give the formulas for the charged and
neutral current cross sections, including also the small non-PCAC transverse
current contributions and taking into account the effect of the \mu^- mass. Our
results are compared with the experimental ones and other theoretical
treatments.Comment: 18 pages, 4 figure
Flavour Physics and CP Violation in the Standard Model and Beyond
We present the invited lectures given at the Third IDPASC School which took
place in Santiago de Compostela in January 2013. The students attending the
school had very different backgrounds, some of them were doing their Ph.D. in
experimental particle physics, others in theory. As a result, and in order to
make the lectures useful for most of the students, we focused on basic topics
of broad interest, avoiding the more technical aspects of Flavour Physics and
CP Violation. We make a brief review of the Standard Model, paying special
attention to the generation of fermion masses and mixing, as well as to CP
violation. We describe some of the simplest extensions of the SM, emphasising
novel flavour aspects which arise in their framework.Comment: Invited talk at the Third IDPASC School 2013, January 21st - February
2nd 2013, Santiago de Compostela, Galiza, Spain; 36 pages, 8 figures, 2
tables; version with few misprints correcte
Analytic Estimates of the QCD Corrections to Neutrino-Nucleus Scattering
We study the QCD corrections to neutrino deep-inelastic scattering on a
nucleus, and analytically estimate their size. For an isoscalar target, we show
that the dominant QCD corrections to the ratio of the neutral- to
charged-current events are suppressed by sin^4 theta_W, where theta_W is the
weak mixing angle. We then discuss the implications for the NuTeV determination
of sin^2 theta_W.Comment: 16 pages, Late
Leptogenesis
I present the theoretical basis for Leptogenesis and its implications for the
structure of the universe. It is suggested that density fluctuations grow
during the transition period and remnants of this effect should be sought in
the universe. The relation between theories with Majorana neutrinos and low
energy phenomena, including oscillations, advanced considerably during the past
two years with a consistent picture developed in several models.Comment: 9 pages, 3 figures.To appear in the proceedings of The IXth
International Symposium on Particles, Strings and Cosmology at the Tata
Institute of Fundamental Research, Mumbai (Bombay), India, during 3-8 January
200
1/N_c Corrections to the Hadronic Matrix Elements of Q_6 and Q_8 in K --> pi pi Decays
We calculate long-distance contributions to the amplitudes A(K^0 --> pi pi,
I) induced by the gluon and the electroweak penguin operators Q_6 and Q_8,
respectively. We use the 1/N_c expansion within the effective chiral lagrangian
for pseudoscalar mesons. In addition, we adopt a modified prescription for the
identification of meson momenta in the chiral loop corrections in order to
achieve a consistent matching to the short-distance part. Our approach leads to
an explicit classification of the loop diagrams into non-factorizable and
factorizable, the scale dependence of the latter being absorbed in the
low-energy coefficients of the effective theory. Along these lines we calculate
the one-loop corrections to the O(p^0) term in the chiral expansion of both
operators. In the numerical results, we obtain moderate corrections to
B_6^(1/2) and a substantial reduction of B_8^(3/2).Comment: 32 pages, LaTeX, 8 eps figures. One reference added, to appear in
Phys. Rev.
Electroweak radiative corrections to deep-inelastic neutrino scattering - implications for NuTeV ?
We calculate the O(alpha) electroweak corrections to charged- and
neutral-current deep-inelastic neutrino scattering off an isoscalar target. The
full one-loop-corrected cross sections, including hard photonic corrections,
are evaluated and compared to an earlier result which was used in the NuTeV
analysis. In particular, we compare results that differ in input-parameter
scheme, treatment of real photon radiation and factorization scheme. The
associated shifts in the theoretical prediction for the ratio of neutral- and
charged-current cross sections can be larger than the experimental accuracy of
the NuTeV result.Comment: 19 pages late
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