32 research outputs found
Monomial transformations of the projective space
We prove that, over any field, the dimension of the indeterminacy locus of a
rational transformation of which is defined by monomials of the same
degree with no common factors is at least , provided that the
degree of as a map is not divisible by . This implies upper bounds on
the multidegree of
Tau anomalous magnetic moment form factor at Super B/Flavor factories
The proposed high-luminosity B/Flavor factories offer new opportunities for
the improved determination of the fundamental physical parameters of standard
heavy leptons. Compared to the electron or the muon case, the magnetic
properties of the lepton are largely unexplored. We show that the
electromagnetic properties of the , and in particular its magnetic form
factor, may be measured competitively in these facilities, using unpolarized or
polarized electron beams. Various observables of the 's produced on top
of the resonances, such as cross-section and normal polarization for
unpolarized electrons or longitudinal and transverse asymmetries for polarized
beams, can be combined in order to increase the sensitivity on the magnetic
moment form factor. In the case of polarized electrons, we identify a special
combination of transverse and longitudinal polarizations able to
disentangle this anomalous magnetic form factor from both the charge form
factor and the interference with the Z-mediating amplitude. For an integrated
luminosity of one could achieve a sensitivity of
about , which is several orders of magnitude below any other existing
high- or low-energy bound on the magnetic moment. Thus one may obtain a QED
test of this fundamental quantity to a few % precision.Comment: 20 pages, 4 figure
Chen-Ruan cohomology of ADE singularities
We study Ruan's \textit{cohomological crepant resolution conjecture} for
orbifolds with transversal ADE singularities. In the -case we compute both
the Chen-Ruan cohomology ring and the quantum corrected
cohomology ring . The former is achieved in general, the
later up to some additional, technical assumptions. We construct an explicit
isomorphism between and in the -case,
verifying Ruan's conjecture. In the -case, the family
is not defined for . This implies that
the conjecture should be slightly modified. We propose a new conjecture in the
-case which we prove in the -case by constructing an explicit
isomorphism.Comment: This is a short version of my Ph.D. Thesis math.AG/0510528. Version
2: chapters 2,3,4 and 5 has been rewritten using the language of groupoids; a
link with the classical McKay correpondence is given. International Journal
of Mathematics (to appear
Quivers from Matrix Factorizations
We discuss how matrix factorizations offer a practical method of computing
the quiver and associated superpotential for a hypersurface singularity. This
method also yields explicit geometrical interpretations of D-branes (i.e.,
quiver representations) on a resolution given in terms of Grassmannians. As an
example we analyze some non-toric singularities which are resolved by a single
CP1 but have "length" greater than one. These examples have a much richer
structure than conifolds. A picture is proposed that relates matrix
factorizations in Landau-Ginzburg theories to the way that matrix
factorizations are used in this paper to perform noncommutative resolutions.Comment: 33 pages, (minor changes
Higgs boson production in photon-photon collision at ILC: a comparative study in different little Higgs models
We study the process \gamma\gamma->h->bb_bar at ILC as a probe of different
little Higgs models, including the simplest little Higgs model (SLH), the
littlest Higgs model (LH), and two types of littlest Higgs models with T-parity
(LHT-I, LHT-II). Compared with the Standard Model (SM) prediction, the
production rate is found to be sizably altered in these little Higgs models
and, more interestingly, different models give different predictions. We find
that the production rate can be possibly enhanced only in the LHT-II for some
part of the parameter space, while in all other cases the rate is suppressed.
The suppression can be 10% in the LH and as much as 60% in both the SLH and the
LHT-I/LHT-II. The severe suppression in the SLH happens for a large \tan\beta
and a small m_h, in which the new decay mode h->\eta\eta (\eta is a light
pseudo-scalar) is dominant; while for the LHT-I/LHT-II the large suppression
occurs when f and m_h are both small so that the new decay mode h->A_H A_H is
dominant. Therefore, the precision measurement of such a production process at
the ILC will allow for a test of these models and even distinguish between
different scenarios.Comment: Version in JHEP (h-g-g & h-gamma-gamma expressions added
Chromomagnetic Dipole Moment of the Top Quark Revisited
We study the complete one-loop contributions to the chromagnetic dipole
moment of the top quark in the Standard Model, two Higgs doublet
models, topcolor assited technicolor models (TC2), 331 models and extended
models with a single extra dimension. We find that the SM predicts
and that the predictions of the other models are also
consitent with the constraints imposed on by low-energy
precision measurements.Comment: 20 pages, 5 figures, Updat
Testing new physics with the electron g-2
We argue that the anomalous magnetic moment of the electron (a_e) can be used
to probe new physics. We show that the present bound on new-physics
contributions to a_e is 8*10^-13, but the sensitivity can be improved by about
an order of magnitude with new measurements of a_e and more refined
determinations of alpha in atomic-physics experiments. Tests on new-physics
effects in a_e can play a crucial role in the interpretation of the observed
discrepancy in the anomalous magnetic moment of the muon (a_mu). In a large
class of models, new contributions to magnetic moments scale with the square of
lepton masses and thus the anomaly in a_mu suggests a new-physics effect in a_e
of (0.7 +- 0.2)*10^-13. We also present examples of new-physics theories in
which this scaling is violated and larger effects in a_e are expected. In such
models the value of a_e is correlated with specific predictions for processes
with violation of lepton number or lepton universality, and with the electric
dipole moment of the electron.Comment: 34 pages, 7 figures. Minor changes and references adde
The Large Hadron-Electron Collider at the HL-LHC
The Large Hadron-Electron Collider (LHeC) is designed to move the field of deep inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting energy-recovery technology, it collides a novel, intense electron beam with a proton or ion beam from the High-Luminosity Large Hadron Collider (HL-LHC). The accelerator and interaction region are designed for concurrent electron-proton and proton-proton operations. This report represents an update to the LHeC's conceptual design report (CDR), published in 2012. It comprises new results on the parton structure of the proton and heavier nuclei, QCD dynamics, and electroweak and top-quark physics. It is shown how the LHeC will open a new chapter of nuclear particle physics by extending the accessible kinematic range of lepton-nucleus scattering by several orders of magnitude. Due to its enhanced luminosity and large energy and the cleanliness of the final hadronic states, the LHeC has a strong Higgs physics programme and its own discovery potential for new physics. Building on the 2012 CDR, this report contains a detailed updated design for the energy-recovery electron linac (ERL), including a new lattice, magnet and superconducting radio-frequency technology, and further components. Challenges of energy recovery are described, and the lower-energy, high-current, three-turn ERL facility, PERLE at Orsay, is presented, which uses the LHeC characteristics serving as a development facility for the design and operation of the LHeC. An updated detector design is presented corresponding to the acceptance, resolution, and calibration goals that arise from the Higgs and parton-density-function physics programmes. This paper also presents novel results for the Future Circular Collider in electron-hadron (FCC-eh) mode, which utilises the same ERL technology to further extend the reach of DIS to even higher centre-of-mass energies.Peer reviewe