C. López

N = 1 supergravity, the weak scale and the low-energy particle spectrum

Abstract We consider in detail the radiative SU(2) × U(1) breaking induced by broken N = 1 supergravity. We include in this study some parameters (b-quark Yukawas, mixed Higgs mass terms) neglected in a previous analysis. We show that there are essentially two types of mechanisms leading to radiative SU(2) × U(1) breaking. The first of them occurs for a t-quarks mass m t ⪆60 GeV. The second one appears for arbitrary small values of mt (without using a large A). These two mechanism correspond to two different classes of local SUSY GUTs. We present results for the low-energy supersymmetric particle spectrum. In some of the possible scenarios presented, squarks, sleptons and/or gauginos are accessible to present accelerator energies. In other scenarios, the scalar neutrinos may be the lightest R-odd particles. We finally remark that the SU(5) prediction for mb/mt is substanially suppressed for a heavy t-quark.

The low-energy supersymmetric spectrum according to N = 1 supergravity guts

Abstract We reexamine the radiative SU(2) × U(1) breaking induced by broken N = 1 supergravity in the light of recent experimental results. Explicit formulae are given for the supersymmetric particle spectrum and the SU(2) × U(1) breaking condition. The experimental results (t-quark mass) constrain the supergravity parameters, particularly the bare higgsino mass μ 0 and the “mixing” Higgs mass term μ 3 2 . Models with globally supersymmetric “observable” sectors (except for gaugino masses) are excluded in their simplest version. If the identity B = A − 1 is assumed, further restrictions on the range of the supergravity parameters are found. The particle spectra leading to possible supersymmetric interpretations of the CERN missing p T events are analyzed. We study in detail the following three scenarios: (i) m q ⋍ 80–140 GeV , M g = 3 GeV ; (ii) q ⋍ M g ⋍ 40 GeV ; (iii) M g = 40 GeV , m q ⪢ M g and give the corresponding spectra of sparticles as a function of the A -parameter.

N=1 supergravity, the breaking of SU(2)×U(1) and the top-quark mass

Abstract Spontaneously broken N=1 supergravity coupled to grand unified theories generates soft terms which break explicitly the residual global supersymmetry. These soft terms characterized by the gravitino mass scale induce radiatively the breaking of the SU(2)×U(1) symmetry. This is achieved for top-quark masses 50 GeV≲mt≲190 GeV. For negligible (susy-breaking) gaugino masses we give an analytical lower bound on mt as a function of the strength of the trilinear scalar couplings (A).

Experimental determination of the energy generated in nuclear cascades by a high energy beam

An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 109 ppp) proton beam from CERN-PS at several kinetic energies from 600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically G ≈ 30 in reasonable agreement with calculations, where G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which G decreases but is still acceptable in the energy range explored

Experimental verification of neutron phenomenology in lead and transmutation by adiabatic resonance crossing in accelerator driven systems

Energy and space distributions of spallation neutrons (from 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3 x 3.3 x 3 m3 lead volume and neutron capture rates on long-lived fission fragments 99 Tc and 129 I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.

How to look for squarks with the p̄p collider

Abstract We consider Drell-Yan-like production of squarks q from pp, starting with a valence quark and gluino from the sea. The signal would be highly energetic jet, E jet ∼ 1 2 m q , and the same amount of missing energy back to back with it. If m( gluino ) ⪅ 16 GeV , m q ∼ 60–160 GeV . The amount of such signals would be some 14 to 1 times that of the signal for p p → ( W → e v ) + all .

Squark production and signals at the p̄p collider

Abstract We consider the signals due to Drell-Yan production of squarks in pp collisions, from a valence quark and a gluino from the sea. We find (i) a bump on the squark mass in two and multijet events; (ii) a certain number of events with jet (quark) and missing p t (photino); (iii) events with one jet (quark), electron/muon and missing p t (photino and neutrino).

Neutron driven nuclear transmutation by adiabatic resonance crossing

The use of accelerator driven system (ADS) like for instance the Energy Amplifier concept (EA) proposed by C. Rubbia and his group might be one of the solutions to solve the energy problem and in particular to answer the question: what could we do with the nuclear waste produced by the present nuclear reactors? We present in this paper the EA concept, which is illustrated by two experiments performed at the CERN-PS facility. One of them is the TARC (Transmutation by Adiabatic Resonance crossing) experiment which is designed to demonstrate the high efficiency offered by the EA to destroy the long-lived fission fragments.

Violations of the Callan-Gross relation as a function of x, Q2 from QCD

Abstract We consider the behaviour of R(x, Q 2 ) ∼ σ L σ T as x → 0 , 1 from QCD. The simplest parametrisation compatible with the behaviour found (exact at x = 0, 1) is R(x,Q 2 )= 4α c (Q 2 ) 3π { 1−x 2+λ s [1+ 3 2 n f (1−x) 2 d + (1+λ s )−D 11 (1+λ s ) (3+λ s )D 12 (1+λ s ) ]+ x 1+ν 0 −(16/3β 0 ) log α c (Q 2 ) }(1−x) , as Q 2 → ∞. d + , D ij are the largest eigenvalue and the matrix elements of D = − γ 0 (n) 2β c valuated at n = 1+λ s .ν 0 = 2.1 ± 0.2 and λ s = 0.37 ± 0.07 are known from existing fits to F 2 alone. For 0⪅ x ⪅0.1 our calculation predicts R ( x , Q 2 )≅(1.8±0.3)/log( Q 2 / Λ 2 ); experimentally, R exp ( x , Q 2 )4)/log( Q 2 / Λ 2 ).

MODEL INDEPENDENT CALCULATION OF Kp DISPERSION RELATIONS.

Abstract Using an extrapolation procedure proposed by one of us, whichn is based on rigorous properties of Pade approximants, we compute forward Kp dispersion relations. Among other results. we get averages of the absorptive part of the amplitude in the unphysical cut, and the absolute bounds 12.39⩽ G 2 /4π⩽16.45 , and statistical estimate and errors G 2 /4π=14.15±1.17 , for the combination G 2 =G pΛK 2 +0.92 G pΣK 2 . This is to be compared with the result of the polynominal extrapolation of Cutkosky and Deo, G 2 /4π=15 −4 +6 , the lower bound of Rogers, G 2 /4gp >/ 10, and a host of model - dependent calculations for which G 2 /4π ranges between 4 and 20.