985 resultados para Supersymmetrie, ATLAS, LHC, GMSB


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For large values of the minimal supergravity model parameter tan beta, the tau lepton and the bottom quark Yukawa couplings become large, leading to reduced masses of tau sleptons and b squarks relative to their first and second generation counterparts, and to enhanced decays of charginos and neutralinos to tau leptons and b quarks. We evaluate the reach of the CERN Large Hadron Collider (LHC) pp collider for supersymmetry in the MSUGRA model parameter space. We find that values of m((g) over tilde) similar to 1500-2000 GeV can be probed with just 10 fb(-1) of integrated luminosity for tan beta values as high as 45, so that MSUGRA cannot escape the scrutiny of LHC experiments by virtue of having a large value of tan beta. We also perform a case study of an MSUGRA model at tan beta = 45 where (Z) over tilde(2)-->tau<(tau)over tilde>(1) and (W) over tilde(1)-->tau(1)nu(tau) with similar to 100% branching fraction. In this case, at least within our simplistic study, we show that a di-tau mass edge, which determines the value of m((Z) over tilde 2) - m((Z) over tilde 1), can still be reconstructed. This information can be used as a starting point for reconstructing SUSY cascade decays on an event-by-event basis, and can provide a strong constraint in determining the underlying model parameters. Finally, we show that for large tan beta, there can be an observable excess of tau leptons, and argue that tau signals might serve to provide new information about the underlying model framework. [S0556-2821(99)04205-8].

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Pós-graduação em Geografia - IGCE

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This monograph is part of the works developed in the Scientific Initiation aimed at updating and improving the Atlas of Brazilian Agrarian Question - AQAB. For pioneering and scope of work-matrix, the objective this first part focused on the development of issues related to agricultural production, being drawn maps with data from the Municipal Agricultural Production-PAM 2012; Municipal Livestock Research-PPM 2012; Production of Vegetable Extraction and Forestry-2012, all analyzed from bibliographic review and joint interpretation of tables and graphs. Pari passu, this topic allowed the development of studies on peasant farms, because they are correlated subjects. Peasant farmers produce large portion of the food served to the population. Its features are its mode of production in the field, the way in which the activities take place within the family, the struggle for their social reproduction and by the earth, the practice of polyculture, preservation of the environment and the genetic diversity of species. The surplus production is sold on the market to meet other family demands unmet by production on their properties. We understand that both terms; Peasant or Farmer, refer to the same subject, but with different interpretations of their way of social reproduction and market relations...

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This monograph is part of the works developed in the Scientific Initiation aimed at updating and improving the Atlas of Brazilian Agrarian Question - AQAB. For pioneering and scope of work-matrix, the objective this first part focused on the development of issues related to agricultural production, being drawn maps with data from the Municipal Agricultural Production-PAM 2012; Municipal Livestock Research-PPM 2012; Production of Vegetable Extraction and Forestry-2012, all analyzed from bibliographic review and joint interpretation of tables and graphs. Pari passu, this topic allowed the development of studies on peasant farms, because they are correlated subjects. Peasant farmers produce large portion of the food served to the population. Its features are its mode of production in the field, the way in which the activities take place within the family, the struggle for their social reproduction and by the earth, the practice of polyculture, preservation of the environment and the genetic diversity of species. The surplus production is sold on the market to meet other family demands unmet by production on their properties. We understand that both terms; Peasant or Farmer, refer to the same subject, but with different interpretations of their way of social reproduction and market relations...

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We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.

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Identical neutral kaon pair correlations are measured in root s = 7 TeV pp collisions in the ALICE experiment. One-dimensional (KsKs0)-K-0 correlation functions in terms of the invariant momentum difference of kaon pairs are formed in two multiplicity and two transverse momentum ranges. The femtoscopic parameters for the radius and correlation strength of the kaon source are extracted. The fit includes quantum statistics and final-state interactions of the a(0)/f(0) resonance. (KsKs0)-K-0 correlations show an increase in radius for increasing multiplicity and a slight decrease in radius for increasing transverse mass, mT, as seen in pi pi correlations in pp collisions and in heavy-ion collisions. Transverse mass scaling is observed between the (KsKs0)-K-0 and pi pi radii. Also, the first observation is made of the decay of the f(2)'(1525) meson into the (KsKs0)-K-0 channel in pp collisions. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.

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In SUSY models with heavy squarks and gaugino mass unification, the gaugino pair production reaction pp -> (W) over tilde (+/-)(1)(Z) over tilde (2) dominates gluino pair production for m (g) over tilde less than or similar to 1 TeV at LHC with root s = 14 TeV (LHC14). For this mass range, the two-body decays (W) over tilde (1) -> W (Z) over tilde (1) and (Z) over tilde (2) -> h (Z) over tilde (1) are expected to dominate the chargino and neutralino branching fractions. By searching for lb (b) over tilde + is not an element of(T) events from (W) over tilde (+/-)(1)Z(2) production, we show that LHC14 with 100 fb(-1) of integrated luminosity becomes sensitive to chargino masses in the range m((W) over tilde1) similar to 450-550 GeV corresponding to m (g) over tilde similar to 1.5-2 TeV in models with gaugino mass unification. For 10(3) fb(-1), LHC14 is sensitive to the Wh channel for m((W) over tilde1) similar to 300-800 GeV, corresponding to m (g) over tilde similar to 1-2.8 TeV, which is comparable to the reach for gluino pair production followed by cascade decays. The Wh + is not an element of(T) search channel opens up a new complementary avenue for SUSY searches at LHC, and serves to point to SUSYas the origin of any new physics discovered via multijet and multilepton + is not an element of(T) channels.

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In the framework of gauged flavour symmetries, new fermions in parity symmetric representations of the standard model are generically needed for the compensation of mixed anomalies. The key point is that their masses are also protected by flavour symmetries and some of them are expected to lie way below the flavour symmetry breaking scale(s), which has to occur many orders of magnitude above the electroweak scale to be compatible with the available data from flavour changing neutral currents and CP violation experiments. We argue that, actually, some of these fermions would plausibly get masses within the LHC range. If they are taken to be heavy quarks and leptons, in (bi)-fundamental representations of the standard model symmetries, their mixings with the light ones are strongly constrained to be very small by electroweak precision data. The alternative chosen here is to exactly forbid such mixings by breaking of flavour symmetries into an exact discrete symmetry, the so-called proton-hexality, primarily suggested to avoid proton decay. As a consequence of the large value needed for the flavour breaking scale, those heavy particles are long-lived and rather appropriate for the current and future searches at the LHC for quasi-stable hadrons and leptons. In fact, the LHC experiments have already started to look for them.

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We extend our earlier results delineating the supersymmetry reach of the CERN Large Hadron Collider operating at a center-of-mass energy root s = 7 TeV to integrated luminosities in the range 5-30 fb(-1). Our results are presented within the paradigm minimal supergravity model or constrained minimal supersymmetric standard model. Using a six-dimensional grid of cuts for the optimization of signal to background ratio-including missing E-T-we find for m((g) over tilde) similar to m((q) over tilde) an LHC 5 sigma supersymmetry discovery reach of m((g) over tilde) similar to 1:3, 1.4, 1.5, and 1.6 TeV for 5, 10, 20, and 30 fb(-1), respectively. For m((q) over tilde) >> m((g) over tilde), the corresponding reach is instead m((g) over tilde) similar to 0: 8, 0.9, 1.0, and 1.05 TeV, for the same integrated luminosities.

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The predictions of Drell-Yan production of low-mass lepton pairs, at high rapidity at the LHC, are known to depend sensitively on the choice of factorization and renormalization scales. We show how this sensitivity can be greatly reduced by fixing the factorization scale of the LO contribution based on the known NLO matrix element, so that observations of this process at the LHC can make direct measurements of parton distribution functions in the low x domain; x less than or similar to 10(-4).

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In the CP-violating Minimal Supersymmetric Standard Model, we study the production of a neutralino-chargino pair at the LHC. For their decays into three leptons, we analyze CP asymmetries which are sensitive to the CP phases of the neutralino and chargino sector. We present analytical formulas for the entire production and decay process, and identify the CP-violating contributions in the spin correlation terms. This allows us to define the optimal CP asymmetries. We present a detailed numerical analysis of the cross sections, branching ratios, and the CP observables. For light neutralinos, charginos, and squarks, the asymmetries can reach several 10%. We estimate the discovery potential for the LHC to observe CP violation in the trilepton channel.

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