6,196 research outputs found
Expectations for LHC from Naturalness: Modified vs. SM Higgs Sector
Common lore has it that naturalness of electroweak breaking in the SM
requires new physics (NP) at Lambda < 2-3 TeV, hopefully within the reach of
LHC. Moreover the Higgs should be light (m_h < 219 GeV) to pass electroweak
precision tests (EWPT). However one should be prepared for "unexpected"
(although admittedly unpleasant) results at LHC, i.e. no NP and/or a heavy
Higgs. We revisit recent attempts to accommodate this by modifying the SM Higgs
sector (using 2-Higgs-doublet models). We find that these models do not improve
the naturalness of the SM, and so they do not change the expectations of
observing NP at LHC. We also stress that a heavy SM Higgs would not be evidence
in favour of a modified Higgs sector, provided certain higher order operators
influence EWPT. On the other hand, we show that NP can escape LHC detection
without a naturalness price, and with the pure SM as the effective theory valid
at LHC energies, simply if the cut-off for top loops is slightly lower than for
Higgs loops.Comment: 37 pages, LaTeX, 13 figure
Breaking the electroweak symmetry and supersymmetry by a compact extra dimension
We revisit in some more detail a recent specific proposal for the breaking of
the electroweak symmetry and of supersymmetry by a compact extra dimension.
Possible mass terms for the Higgs and the matter hypermultiplets are considered
and their effects on the spectrum analyzed. Previous conclusions are reinforced
and put on firmer ground.Comment: 25 pages, LaTeX, 9 eps figure
Softly Broken Supersymmetric Desert from Orbifold Compactification
A new viewpoint for the gauge hierarchy problem is proposed: compactification
at a large scale, 1/R, leads to a low energy effective theory with
supersymmetry softly broken at a much lower scale, \alpha/R. The hierarchy is
induced by an extremely small angle \alpha which appears in the orbifold
compactification boundary conditions. The same orbifold boundary conditions
break Peccei-Quinn symmetry, leading to a new solution to the \mu problem.
Explicit 5d theories are constructed with gauge groups SU(3) \times SU(2)
\times U(1) and SU(5), with matter in the bulk or on the brane, which lead to
the (next-to) minimal supersymmetric standard model below the compactification
scale. In all cases the soft supersymmetry-breaking and \mu parameters
originate from bulk kinetic energy terms, and are highly constrained. The
supersymmetric flavor and CP problems are solved.Comment: 18 pages, Latex, corrected values for A parameter
Experimental method for measuring classical concurrence of generic beam shapes
Classical entanglement is a powerful tool which provides a neat numerical
estimate for the study of classical correlations. Its experimental
investigation, however, has been limited to special cases. Here, we demonstrate
that the experimental quantification of the level of classical entanglement can
be carried out in more general instances. Our approach enables the extension to
arbitrarily shaped transverse modes and hence delivering a suitable
quantification tool to describe concisely the modal structure
The Median Probability Model and Correlated Variables
The median probability model (MPM) Barbieri and Berger (2004) is defined as
the model consisting of those variables whose marginal posterior probability of
inclusion is at least 0.5. The MPM rule yields the best single model for
prediction in orthogonal and nested correlated designs. This result was
originally conceived under a specific class of priors, such as the point mass
mixtures of non-informative and g-type priors. The MPM rule, however, has
become so very popular that it is now being deployed for a wider variety of
priors and under correlated designs, where the properties of MPM are not yet
completely understood. The main thrust of this work is to shed light on
properties of MPM in these contexts by (a) characterizing situations when MPM
is still safe under correlated designs, (b) providing significant
generalizations of MPM to a broader class of priors (such as continuous
spike-and-slab priors). We also provide new supporting evidence for the
suitability of g-priors, as opposed to independent product priors, using new
predictive matching arguments. Furthermore, we emphasize the importance of
prior model probabilities and highlight the merits of non-uniform prior
probability assignments using the notion of model aggregates
The LHC (CMS) Discovery Potential for Models with Effective Supersymmetry and Nonuniversal Gaugino Masses
We investigate squark and gluino pair production at LHC (CMS) with subsequent
decays into quarks, leptons and LSP in models with effective supersymmetry
where third generation of squarks is relatively light while the first two
generations of squarks are heavy. We consider the general case of nonuniversal
gaugino masses. Visibility of signal by an excess over SM background in (n \geq
2)jets + (m \geq 0)leptons + E^{miss}_T events depends rather strongly on the
relation between LSP, second neutralino, gluino and squark masses and it
decreases with the increase of LSP mass. We find that for relatively heavy
gluino it is very difficult to detect SUSY signal even for light 3^{rd}
generation squarks (m_{\tilde q_3}\le 1 TeV) if the LSP mass is closed to the
3^{rd} generation squark mass.Comment: 1 latex (35 pages), 4 eps (figures) file
New Physics and CP Violation in Singly Cabibbo Suppressed D Decays
We analyze various theoretical aspects of CP violation in singly Cabibbo
suppressed (SCS) D-meson decays, such as . In particular, we
explore the possibility that CP asymmetries will be measured close to the
present level of experimental sensitivity of . Such measurements
would signal new physics. We make the following points: (i) The mechanism at
work in neutral D decays could be indirect or direct CP violation (or both).
(ii) One can experimentally distinguish between these possibilities. (iii) If
the dominant CP violation is indirect, then there are clear predictions for
other modes. (iv) Tree-level direct CP violation in various known models is
constrained to be much smaller than . (v) SCS decays, unlike Cabibbo
favored or doubly Cabibbo suppressed decays, are sensitive to new contributions
from QCD penguin operators and especially from chromomagnetic dipole operators.
This point is illustrated with supersymmetric gluino-squark loops, which can
yield direct CP violating effects of .Comment: 36 pages, 5 figure
Comets
The paper reviews properties of comets, from historical sightings and interpretations, to contemporary ground- and space-based knowledge. The importance of comets in understanding the present Solar System and its dynamical, physical and chemical evolution, their relationship with other minor bodies, their possible role for the very early phases of our Earth, will be examined. Emphasis will be on the results of the recently completed European Rosetta mission to comet 67P/Churyumov-Gerasimenko, in particular those by OSIRIS, its imaging system. It is fair to say that Rosetta's results represent a most important step in the development of cometary science, whose full implications start just to surface and will be fully appreciated over several more years
SN1987A - a Testing Ground for the KARMEN Anomaly
We show, that SN1987A can serve as an astrophysical laboratory for testing
the viability of the assertion that a new massive neutral fermion is implied by
the KARMEN data. We show that a wide range of the parameters characterizing the
proposed particle is ruled out by the above constraints making this
interpretation very unlikely.Comment: 12 pages, 1 eps figure embedded, to appear in Phys. Lett.
Up Quark Masses from Down Quark Masses
The quark and charged lepton masses and the angles and phase of the CKM
mixing matrix are nicely reproduced in a model which assumes SU(3)xSU(3)
flavour symmetry broken by the v.e.v.'s of fields in its bi-fundamental
representation. The relations among the quark mass eigenvalues, m_u/m_c \approx
m_c/m_t \approx m^2_d/m^2_s \approx m^2_s/m^2_b \approx
\Lambda^2_{GUT}/M^2_{Pl}, follow from the broken flavour symmetry. Large
tan(beta) is required which also provides the best fits to data for the
obtained textures. Lepton-quark grandunification with a field that breaks both
SU(5) and the flavour group correctly extends the predictions to the charged
lepton masses. The seesaw extension of the model to the neutrino sector
predicts a Majorana mass matrix quadratically hierarchical as compared to the
neutrino Dirac mass matrix, naturally yielding large mixings and low mass
hierarchy for neutrinos.Comment: 11 pages, 1 figure. Published version: model improved, references
adde
- …