2,546 research outputs found
Quality of a Which-Way Detector
We introduce a measure Q of the "quality" of a quantum which-way detector,
which characterizes its intrinsic ability to extract which-way information in
an asymmetric two-way interferometer. The "quality" Q allows one to separate
the contribution to the distinguishability of the ways arising from the quantum
properties of the detector from the contribution stemming from a-priori
which-way knowledge available to the experimenter, which can be quantified by a
predictability parameter P. We provide an inequality relating these two sources
of which-way information to the value of the fringe visibility displayed by the
interferometer. We show that this inequality is an expression of duality,
allowing one to trace the loss of coherence to the two reservoirs of which-way
information represented by Q and P. Finally, we illustrate the formalism with
the use of a quantum logic gate: the Symmetric Quanton-Detecton System (SQDS).
The SQDS can be regarded as two qubits trying to acquire which way information
about each other. The SQDS will provide an illustrating example of the
reciprocal effects induced by duality between system and which-way detector.Comment: 10 pages, 5 figure
Ditau jets in Higgs searches
Understanding and identifying ditau jets -- jets consisting of pairs of tau
particles, can be of crucial importance and may even turn out to be a necessity
if the Higgs boson decays dominantly to new light scalars which, on the other
hand, decay to tau pairs. As often seen in various models of BSM such as in the
NMSSM, Higgs portals etc., the lightness of these new states ensures their
large transverse momenta and, as a consequence, the collinearity of their decay
products. We show that the non-standard signatures of these objects, which can
easily be missed by standard analysis techniques, can be superbly exploited in
an analysis based on subjet observables. When combined with additional
selection strategies, this analysis can even facilitate an early discovery of
the Higgs boson. To be specific, a light Higgs can be found with from of data. We combine all these
observables into a single discriminating likelihood that can be employed toward
the construction of a realistic and standalone ditau tagger.Comment: 9 pages, 9 figures. References added, typos corrected, published
versio
E10 and SO(9,9) invariant supergravity
We show that (massive) D=10 type IIA supergravity possesses a hidden rigid
SO(9,9) symmetry and a hidden local SO(9) x SO(9) symmetry upon dimensional
reduction to one (time-like) dimension. We explicitly construct the associated
locally supersymmetric Lagrangian in one dimension, and show that its bosonic
sector, including the mass term, can be equivalently described by a truncation
of an E10/K(E10) non-linear sigma-model to the level \ell<=2 sector in a
decomposition of E10 under its so(9,9) subalgebra. This decomposition is
presented up to level 10, and the even and odd level sectors are identified
tentatively with the Neveu--Schwarz and Ramond sectors, respectively. Further
truncation to the level \ell=0 sector yields a model related to the reduction
of D=10 type I supergravity. The hyperbolic Kac--Moody algebra DE10, associated
to the latter, is shown to be a proper subalgebra of E10, in accord with the
embedding of type I into type IIA supergravity. The corresponding decomposition
of DE10 under so(9,9) is presented up to level 5.Comment: 1+39 pages LaTeX2e, 2 figures, 2 tables, extended tables obtainable
by downloading sourc
Interacting Bosons at Finite Temperature: How Bogolubov Visited a Black Hole and Came Home Again
The structure of the thermal equilibrium state of a weakly interacting Bose
gas is of current interest. We calculate the density matrix of that state in
two ways. The most effective method, in terms of yielding a simple, explicit
answer, is to construct a generating function within the traditional framework
of quantum statistical mechanics. The alternative method, arguably more
interesting, is to construct the thermal state as a vector state in an
artificial system with twice as many degrees of freedom. It is well known that
this construction has an actual physical realization in the quantum
thermodynamics of black holes, where the added degrees of freedom correspond to
the second sheet of the Kruskal manifold and the thermal vector state is a
state of the Unruh or the Hartle-Hawking type. What is unusual about the
present work is that the Bogolubov transformation used to construct the thermal
state combines in a rather symmetrical way with Bogolubov's original
transformation of the same form, used to implement the interaction of the
nonideal gas in linear approximation. In addition to providing a density
matrix, the method makes it possible to calculate efficiently certain
expectation values directly in terms of the thermal vector state of the doubled
system.Comment: 25 pages, LaTeX. To appear in a special issue of Foundations of
Physics in honor of Jacob Bekenstei
G+++ Invariant Formulation of Gravity and M-Theories: Exact BPS Solutions
We present a tentative formulation of theories of gravity with suitable
matter content, including in particular pure gravity in D dimensions, the
bosonic effective actions of M-theory and of the bosonic string, in terms of
actions invariant under very-extended Kac-Moody algebras G+++. We conjecture
that they host additional degrees of freedom not contained in the conventional
theories. The actions are constructed in a recursive way from a level expansion
for all very-extended algebras G+++. They constitute non-linear realisations on
cosets, a priori unrelated to space-time, obtained from a modified Chevalley
involution. Exact solutions are found for all G+++. They describe the algebraic
properties of BPS extremal branes, Kaluza-Klein waves and Kaluza-Klein
monopoles. They illustrate the generalisation to all G+++ invariant theories of
the well-known duality properties of string theories by expressing duality as
Weyl invariance in G+++. Space-time is expected to be generated dynamically. In
the level decomposition of E8+++ = E11, one may indeed select an A10
representation of generators Pa which appears to engender space-time
translations by inducing infinite towers of fields interpretable as field
derivatives in space and time.Comment: Latex 45 pages, 1 figure. Discussion on pages 19 and 20 altered.
Appendix B amplified. 4 footnotes added. 2 references added. Acknowledgments
updated. Additional minor correction
Hierarchy of inequalities for quantitative duality
We derive different relations quantifying duality in a generic two-way
interferometer. These relations set different upper bounds to the visibility V
of the fringes measured at the output port of the interferometer. A hierarchy
of inequalities is presented which exhibits the influence of the availability
to the experimenter of different sources of which-way information contributing
to the total distinguishability D of the ways. For mixed states and unbalanced
interferometers an inequality is derived, V^2+ Xi^2 \leq 1, which can be more
stringent than the one associated with the distinguishability (V^2+ D^2 \leq
1).Comment: 7 pages, 4 figure
Black Hole Horizon Fluctuations
It is generally admitted that gravitational interactions become large at an
invariant distance of order from the black hole horizon. We show that due
to the ``atmosphere'' of high angular particles near the horizon strong
gravitational interactions already occur at an invariant distance of the order
of . The implications of these results for the origin of black
hole radiation, the meaning of black hole entropy and the information puzzle
are discussed.Comment: Latex, 22 pages (minor corrections and precisions added
Simulation of cosmic irradiation conditions in thick target arrangements
One approach to simulate 2-pi irradiation conditions of planetary surfaces which has been widely applied in the past are bombardments of so called thick targets. A very large thick target was exposed recently to 2.1 GeV protons at the Bevatron-Bevalac in Berkeley. In a 100x100x180 cm steel-surrounded granodiorite target radioactive medium and high energy spallation products of the incident primary and of secondary particles were analyzed along the beam axis down to depths of 140 g/cm(2) in targets such as Cu, Ni, Co, Fe, T, Si, SiO2 and Al. Activities of these nuclides were exclusively determined via instrumental gamma-ray spectroscopy. Relative yields of neutron capture and spallation products induced in Co and Cu targets during the thick target bombardment are shown as a function of depth. The majority of the medium energy products such as Co-58 from Co targets exhibit a maximum at shallow depths of 40-60 g/cm(2) and then decrease exponentially. In a comparable 600 MeV proton bombarded thick target such a slight maximum for medium energy products was not observed. Rather, Co-58 activities in Co decreased steadily with the highest activity at the surface. The activities of the n-capture product Co-60 increase steadily starting at the surface. This indicates the rapidly growing flux of low energy neutrons within the target
QCD Corrections to Vector-Boson Fusion Processes in Warped Higgsless Models
We discuss the signatures of a representative Higgsless model with ideal
fermion delocalization in vector-boson fusion processes, focusing on the gold-
and silver-plated decay modes of the gauge bosons at the CERN-Large Hadron
Collider. For this purpose, we have developed a fully-flexible parton-level
Monte-Carlo program, which allows for the calculation of cross sections and
kinematic distributions within experimentally feasible selection cuts at
NLO-QCD accuracy. We find that Kaluza-Klein resonances give rise to very
distinctive distributions of the decay leptons. Similar to the Standard Model
case, within the Higgsless scenario the perturbative treatment of the
vector-boson scattering processes is under excellent control.Comment: 22 pages, 20 figure
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