8,002 research outputs found
Speculations on Isolated Lepton Events at HERA
Speculations on mechanisms which might be responsible for events with an
isolated high p_T lepton, a hadron jet and missing energy, as observed in the
H1 experiment at HERA, are discussed.Comment: LaTeX, 6 pages, 2 figures, presented at the XXXI Conference of
Theoretical Physics "Matter to the Deepest", Ustron, Poland, September 5-11,
200
Minimum Weight Flat Antichains of Subsets
Building on classical theorems of Sperner and Kruskal-Katona, we investigate
antichains in the Boolean lattice of all subsets of
, where is flat, meaning that it contains
sets of at most two consecutive sizes, say , where contains only -subsets,
while contains only -subsets. Moreover, we assume
consists of the first -subsets in squashed
(colexicographic) order, while consists of all -subsets
not contained in the subsets in . Given reals , we
say the weight of is
. We characterize the minimum
weight antichains for any given , and we do the
same when in addition is a maximal antichain. We can then derive
asymptotic results on both the minimum size and the minimum Lubell function
The Mott insulator - 10th order perturbation theory extended to infinite order using QMC
We present a new method, based on the combination of analytical and numerical
techniques within the framework of the dynamical mean-field theory (DMFT).
Building upon numerically exact results obtained in an improved quantum Monte
Carlo (QMC) scheme, 10th order strong-coupling perturbation theory for the
Hubbard model on the Bethe lattice is extrapolated to infinite order. We obtain
continuous estimates of energy E and double occupancy D with unprecedented
precision O(10^{-5}) for the Mott insulator above its stability edge
U_{c1}=4.78 as well as critical exponents. The relevance for recent experiments
on Cr-doped V_2O_3 is pointed out.Comment: 4 pages, 5 figures. Significant changes in introduction and summary;
experimental reference added; Figs. 1 and 3 modifie
The W_L W_L scattering at the LHC: improving the selection criteria
We present a systematic study of the different mechanisms leading to WW pair
production at the LHC, both in the same-sign and opposite-sign channels, and we
emphasize that the former offers much better potential for investigating
non-resonant W_L W_L scattering. We propose a new kinematic variable to isolate
the W_L W_L scattering component in same-sign WW production at the LHC.
Focusing on purely leptonic W decay channels, we show that it considerably
improves the LHC capabilities to shed light on the electroweak symmetry
breaking mechanism after collecting 100 fb^{-1} of data at sqrt{s} = 14 TeV.
The new variable is less effective in the opposite-sign WW channel due to
different background composition.Comment: 25 pages, 32 figure
Supersymmetry with R-Parity Breaking: Contact Interactions and Resonance Formation in Leptonic Processes at LEP2
In supersymmetric theories with R-parity breaking, trilinear couplings of two
leptons to scalar sleptons are possible. In electron-positron collisions such
interactions would manifest themselves through contact terms in Bhabha
scattering and in annihilation to mu or tau pair Interpreting the high x, high
Q2 DIS HERA events as charm squark production with squark masses of order 200
GeV, the formation of tau sneutrinos with a mass in the range close to the LEP2
energy or even in reach, is an exciting speculation which can be investigated
in the coming LEP2 runs with energies close to 200 GeV.Comment: 13 pages, LaTex file with 3 figures, uses axodraw.sty (included).
References updated / limits from rare B decays on Yukawa couplings updated,
favoring tau-sneutrinos over mu-sneutrinos/ numerical results unchange
Leptoquark/Squark Interpretation of HERA Events: Virtual Effects in e+e- Annihilation to Hadrons
In reference to the recently observed high Q^2, large x events in
deep-inelastic positron-proton scattering at HERA, various leptoquark and
supersymmetric scenarios are discussed. We study the impact of virtual
leptoquark or R-parity breaking squark exchange as well as generic contact
interaction on the production of quark-antiquark pairs in
annihilation, in particular at LEP2.Comment: LaTeX file, 20 pages, 7 figures, uses epsfig, typos fixed, a few
general references adde
R-Parity Violating SUSY Signals in Lepton-Pair Production at the Tevatron
In supersymmetric theories with R-parity breaking, sleptons can be produced
in quark-antiquark annihilation at the Tevatron through interactions in which
two quark fields are coupled to a slepton field. If at the same time trilinear
slepton-lepton-lepton couplings are present, the sleptons can be searched for
as resonances in and final states. Existing Tevatron data can be exploited to derive bounds on the
Yukawa couplings of sleptons to quark and lepton pairs. Similar bounds can also
be obtained from annihilation to hadrons at LEP2.Comment: LaTeX file, 12 pages, 4 figures, uses epsfig, axodra
Bose Condensation and the BTZ Black Hole
Although all popular approaches to quantum gravity are able to recover the
Bekenstein-Hawking entropy-area law in the thermodynamic limit, there are
significant differences in their descriptions of the microstates and in the
application of statistics. Therefore they can have significantly different
phenomenological implications. For example, requiring indistinguishability of
the elementary degrees of freedom should lead to changes in the black hole's
radiative porperties away from the thermodynamic limit and at low temperatures.
We demonstrate this for the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole. The
energy eigenstates and statistical entropy in the thermodynamic limit of the
BTZ black hole were obtained earlier by us via symmetry reduced canonical
quantum gravity. In that model the BTZ black hole behaves as a system of
Bosonic mass shells moving in a one dimensional harmonic trap. Bose
condensation does not occur in the thermodynamic limit but this system
possesses a finite critical temperature, , and exhibits a large condensate
fraction below when the number of shells is finite.Comment: 5 pages, 5 figures. Published versio
Adaptive Boolean Networks and Minority Games with Time--Dependent Capacities
In this paper we consider a network of boolean agents that compete for a
limited resource. The agents play the so called Generalized Minority Game where
the capacity level is allowed to vary externally. We study the properties of
such a system for different values of the mean connectivity of the network,
and show that the system with K=2 shows a high degree of coordination for
relatively large variations of the capacity level.Comment: 4 pages, 4 figure
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