10,413 research outputs found
On the Inversion of High Energy Proton
Inversion of the K-fold stochastic autoconvolution integral equation is an
elementary nonlinear problem, yet there are no de facto methods to solve it
with finite statistics. To fix this problem, we introduce a novel inverse
algorithm based on a combination of minimization of relative entropy, the Fast
Fourier Transform and a recursive version of Efron's bootstrap. This gives us
power to obtain new perspectives on non-perturbative high energy QCD, such as
probing the ab initio principles underlying the approximately negative binomial
distributions of observed charged particle final state multiplicities, related
to multiparton interactions, the fluctuating structure and profile of proton
and diffraction. As a proof-of-concept, we apply the algorithm to ALICE
proton-proton charged particle multiplicity measurements done at different
center-of-mass energies and fiducial pseudorapidity intervals at the LHC,
available on HEPData. A strong double peak structure emerges from the
inversion, barely visible without it.Comment: 29 pages, 10 figures, v2: extended analysis (re-projection ratios,
2D
Extending the Matrix Element Method beyond the Born approximation: Calculating event weights at next-to-leading order accuracy
In this article we illustrate how event weights for jet events can be
calculated efficiently at next-to-leading order (NLO) accuracy in QCD. This is
a crucial prerequisite for the application of the Matrix Element Method in NLO.
We modify the recombination procedure used in jet algorithms, to allow a
factorisation of the phase space for the real corrections into resolved and
unresolved regions. Using an appropriate infrared regulator the latter can be
integrated numerically. As illustration, we reproduce differential
distributions at NLO for two sample processes. As further application and proof
of concept, we apply the Matrix Element Method in NLO accuracy to the mass
determination of top quarks produced in e+e- annihilation. This analysis is
relevant for a future Linear Collider. We observe a significant shift in the
extracted mass depending on whether the Matrix Element Method is used in
leading or next-to-leading order.Comment: 35 pages, 12 figures, references & acknowledgments added, typos
corrected, matches published versio
Fermion-parity duality and energy relaxation in interacting open systems
We study the transient heat current out of a confined electron system into a
weakly coupled electrode in response to a voltage switch. We show that the
decay of the Coulomb interaction energy for this repulsive system exhibits
signatures of electron-electron attraction, and is governed by an
interaction-independent rate. This can only be understood from a general
duality that relates the non-unitary evolution of a quantum system to that of a
dual model with inverted energies. Deriving from the fermion-parity
superselection postulate, this duality applies to a large class of open
systems.Comment: 5 pages + 19 pages of Supplementary Materia
Modelling stochastic mortality for dependent lives
Stochastic mortality, i.e. modelling death arrival via a jump process with stochastic intensity, is gaining increasing reputation as a way to rep- resent mortality risk. This paper represents a .rst attempt to model the mortality risk of couples of individuals, according to the stochastic inten- sity approach. We extend to couples the Cox processes set up, namely the idea that mortality is driven by a jump process whose intensity is itself a stochastic process, proper of a particular generation within each gen- der. Dependence between the survival times of the members of a couple is captured by an Archimedean copula. We also provide a methodology for fitting the joint survival function by working separately on the (analytical) copula and the (analytical) mar- gins. First, we calibrate and select the best fit copula according to the methodology of Wang and Wells (2000b) for censored data. Then, we provide a sample-based calibration for the intensity, using a time- homogeneous, non mean-reverting, affine process: this gives the marginal survival functions. By coupling the best fit copula with the calibrated mar- gins we obtain a joint survival function which incorporates the stochastic nature of mortality improvements. Several measures of time dependent association can be computed out of it. We apply the methodology to a well known insurance dataset, using a sample generation. The best fit copula turns out to be a Nelsen one, which implies not only positive dependency, but dependency increasing with age.stochastic mortality, bivariate mortality, copula functions, longevity risk.
Radiation-Induced Magnetoresistance Oscillations in a 2D Electron Gas
Recent measurements of a 2D electron gas subjected to microwave radiation
reveal a magnetoresistance with an oscillatory dependence on the ratio of
radiation frequency to cyclotron frequency. We perform a diagrammatic
calculation and find radiation-induced resistivity oscillations with the
correct period and phase. Results are explained via a simple picture of current
induced by photo-excited disorder-scattered electrons. The oscillations
increase with radiation intensity, easily exceeding the dark resistivity and
resulting in negative-resistivity minima. At high intensity, we identify
additional features, likely due to multi-photon processes, which have yet to be
observed experimentally.Comment: 5 pages, 3 figures; final version as published in Phys Rev Let
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