800 research outputs found
Initial results from the HARP experiment at CERN
Initial results on particle yields obtained by the HARP experiment are
presented. The measurements correspond to proton--nucleus collisions at beam
energies of 12.9 and for a thin Al target of 5% interacion legth. The
angular range considered is between 10 and 250 . This results are the
first step in the upcoming measurement of the forward production cross-section
for the same target and beam energy, relevant for the calculation of the
far--to--near ratio of the K2K experiment.Comment: Presented at the Neutrino 2004 Internation Conferenc
Supersymmetry Breaking Vacua from M Theory Fivebranes
We consider intersecting brane configurations realizing N=2 supersymmetric
gauge theories broken to N=1 by multitrace superpotentials, and softly to N=0.
We analyze, in the framework of M5-brane wrapping a curve, the supersymmetric
vacua and the analogs of spontaneous supersymmetry breaking and soft
supersymmetry breaking in gauge theories. We show that the M5-brane does not
exhibit the analog of metastable spontaneous supersymmetry breaking, and does
not have non-holomorphic minimal volume curves with holomorphic boundary
conditions. However, we find that any point in the N=2 moduli space can be
rotated to a non-holomorphic minimal volume curve, whose boundary conditions
break supersymmetry. We interpret these as the analogs of soft supersymmetry
breaking vacua in the gauge theory.Comment: 32 pages, 8 figures, harvmac; v2: corrections in eq. 3.6 and in
section 6, reference adde
Meta-Stable Brane Configurations by Adding an Orientifold-Plane to Giveon-Kutasov
In hep-th/0703135, they have found the type IIA intersecting brane
configuration where there exist three NS5-branes, D4-branes and anti-D4-branes.
By analyzing the gravitational interaction for the D4-branes in the background
of the NS5-branes, the phase structures in different regions of the parameter
space were studied in the context of classical string theory. In this paper, by
adding the orientifold 4-plane and 6-plane to the above brane configuration, we
describe the intersecting brane configurations of type IIA string theory
corresponding to the meta-stable nonsupersymmetric vacua of these gauge
theories.Comment: 21 pp, 6 figures; reduced bytes of figures, DBI action analysis added
and to appear in JHE
Geometrically Induced Phase Transitions at Large N
Utilizing the large N dual description of a metastable system of branes and
anti-branes wrapping rigid homologous S^2's in a non-compact Calabi-Yau
threefold, we study phase transitions induced by changing the positions of the
S^2's. At leading order in 1/N the effective potential for this system is
computed by the planar limit of an auxiliary matrix model. Beginning at the two
loop correction, the degenerate vacuum energy density of the discrete confining
vacua split, and a potential is generated for the axion. Changing the relative
positions of the S^2's causes discrete jumps in the energetically preferred
confining vacuum and can also obstruct direct brane/anti-brane annihilation
processes. The branes must hop to nearby S^2's before annihilating, thus
significantly increasing the lifetime of the corresponding non-supersymmetric
vacua. We also speculate that misaligned metastable glueball phases may
generate a repulsive inter-brane force which stabilizes the radial mode present
in compact Calabi-Yau threefolds.Comment: 47 pages, 7 figure
Recommended from our members
Physical Modeling for Dynamic Control of Melting Process in Direct-SLS
During the melting process by laser irradiation, it is essential to understand the
phase change processes to get high quality Direct SLS parts especially when highorder scanning paths are needed. This process is a transient three -dimensional heat
conduction problem with a moving heat source and a moving phase boundary. The
process can be simplified to a one-dimensional moving boundary model using
appropriate assumptions. To implement a real-time control strategy, approximate
solutions were found using three methods. Experiments using a CW CO2 laser were
performed on low carbon steelsamples to verify the models’ results. By using first
order differential equations derived from the model, multi-input multi-output (MIMO)
control strategies can be applied.Mechanical Engineerin
On supersymmetry breaking in string theory from gauge theory in a throat
We embed the supersymmetry breaking mechanism in N=1 SQCD of hep-th/0602239
in a smooth superstring theory using D-branes in the background R^4 \times
SL(2)_{k=1}/U(1) which smoothly captures the throat region of an intersecting
NS5-brane configuration. A controllable deformation of the supersymmetric
branes gives rise to the mass deformation of the magnetic SQCD theory on the
branes. The consequent instability on the open string worldsheet can be
followed onto a stable non-supersymmetric configuration of D-branes which
realize the metastable vacuum configuration in the field theory. The new brane
configuration is shown to backreact onto the background such as to produce
different boundary conditions for the string fields in the radial direction
compared to the supersymmetric configuration. In the string theory, this is
interpreted to mean that the supersymmetry breaking is explicit rather than
spontaneous.Comment: 29 pages, harvmac, 8 figures; v2 typos corrected, reference adde
A new parametrization of the neutrino mixing matrix for neutrino oscillations
In this paper we study three active neutrino oscillations, favored by recent
data from SuperK and SNO, using a new parametrization of the lepton mixing
matrix constructed from a linear combination of the unit matrix , and a
hermitian unitary matrix , that is, .
There are only three real parameters in including the parameter .
It is interesting to find that experimental data on atmospheric neutrino
dictates the angle to be such that the and
mixing is maximal. The solar neutrino problem is solved via the MSW
effect with a small mixing angle, with depending on one small parameter
. The resulting mixing matrix with just two parameters ( and
) predicts that the oscillating probabilities for
and to be equal and of the order . The measurement of CP asymmetries at the proposed Neutrino
Factories would also provide a test of our parametrization.Comment: 10 pages, Retex, no figure
Correlated Errors in Quantum Error Corrections
We show that errors are not generated correlatedly provided that quantum bits
do not directly interact with (or couple to) each other. Generally, this
no-qubits-interaction condition is assumed except for the case where two-qubit
gate operation is being performed. In particular, the no-qubits-interaction
condition is satisfied in the collective decoherence models. Thus, errors are
not correlated in the collective decoherence. Consequently, we can say that
current quantum error correcting codes which correct single-qubit-errors will
work in most cases including the collective decoherence.Comment: no correction, 3 pages, RevTe
Entangled Quantum Clocks for Measuring Proper-Time Difference
We report that entangled pairs of quantum clocks (non-degenerate quantum
bits) can be used as a specialized detector for precisely measuring difference
of proper-times that each constituent quantum clock experiences. We describe
why the proposed scheme would be more precise in the measurement of proper-time
difference than a scheme of two-separate-quantum-clocks. We consider
possibilities that the proposed scheme can be used in precision test of the
relativity theory.Comment: no correction, 4 pages, RevTe
Neutrino oscillation physics with a higher -beam
The precision measurement and discovery potential of a neutrino factory based
on a storage ring of boosted radioactive ions (-beam) is re-examined. In
contrast with past designs, which assume ion factors of and
baselines of L=130 km, we emphasize the advantages of boosting the ions to
higher and increasing the baseline proportionally. In particular, we
consider a medium- scenario (, L=730 km) and a
high- scenario (, L = 3000 km).The increase in
statistics, which grow linearly with the average beam energy, the ability to
exploit the energy dependence of the signal and the sizable matter effects at
this longer baseline all increase the discovery potential of such a machine
very significantly.Comment: An error corrected, conclusions unchanged. Revised version to appear
in Nuclear Physics
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