Multichannel search for minimal supergravity atpp¯ande+e−

Abstract

We examine the phenomenology of minimal supergravity models, assuming only that the low energy theory has the minimal particle content, that electroweak symmetry is radiatively broken, and that R-parity is essentially conserved. After delineating regions of supergravity parameter space currently excluded by direct particle searches at LEP and the Tevatron, we quantify how this search region will be expanded when LEP II and the Tevatron Main Injector upgrades become operational. We describe how various experimental analyses can be consistently combined within a single framework, resulting in a multi-channel search for supersymmetry, but note that this analysis is sensitive to specific assumptions about physics at the unification scale.Typeset using REVT E X 1 Grand Unified Theories (GUTs) [1] provide an attractive synthesis of all gauge interactions. A striking prediction of these models is that the proton is unstable. While the observed stability of the proton can be understood if the GUT scale M X > ∼ 10 16 GeV, the origin and stability of the tiny ratio M W /M X ∼ 10 −14 remain unexplained. Supersymmetry (SUSY) [2] provides an elegant mechanism for the stability of the hierarchy between the two scales provided that supersymmetric particles are lighter than ∼ 1 TeV. More recently, the realization [3] that the precision measurements of the gauge couplings in experiments at LEP are consistent with the simplest SUSY SU(5) GUT (with M SU SY ∼ 1 TeV) but incompatible with minimal non-SUSY SU(5) has motivated many authors [4] to reexamine the expectations of sparticle masses within the theoretically appealing, and relatively strongly constrained, supergravity (SUGRA) framework. Studies of nucleon decay [5] as well as the collider phenomenology [6] of these models have also appeared.Part of the appeal of these models lies in their economy. The masses and couplings of all the sparticles are fixed in terms of just four additional parameters, renormalized at some ultra-high scale at which the physics is very simple. These parameters may be taken [2] to be the common values of soft SUSY-breaking trilinear and bilinear couplings (A 0 and B 0 ), a common SUSY-breaking scalar mass (m 0 ), and a common SUSY-breaking mass for the gauginos of the unbroken grand unified group (m 1/2 ). For phenomenological analyses, however, masses and couplings renormalized at the weak scale are required. These can be readily obtained from the unification scale parameters using renormalization group (RG) techniques [7]. This RG evolution leads [2] to calculable splittings between the masses of the gluinos and the electroweak gauginos and between the squarks and sleptons. Unlike third generation sfermions, the first two generations of squarks are approximately degenerate, consistent with the absence of flavor-changing neutral currents in the K-meson sector. A particular attraction of this framework is that electroweak gauge symmetry is automatically broken down to electromagnetism when the Higgs doublet masses are evolved down to the wea...

Implications of naturalness for the heavy Higgs bosons of supersymmetry

“…To evaluate the range of m A expected by naturalness, we will generate SUSY spectra using Isajet [34,35] in the 2-parameter non-universal Higgs model [36] (NUHM2) which allows for very low values of ∆ EW < 10 (numerous other constrained models are evaluated in Ref. [20] and always give much higher EW fine-tuning).…”

Cosmic X-ray and gamma-ray background from dark matter annihilation

“…It belongs to the so-called "bulk region" within the mSUGRA 5-dimensional parameter space that is consistent with current constraints on the relic density of neutralinos (if neutralinos make up for all the observationally inferred dark matter density). We obtain the photon, electron and positron yields for this model using the numerical code DarkSUSY [43,44] with the interface ISAJET [45].…”

Search for nonpointing and delayed photons in the diphoton and missing transverse momentum final state in 8 TeVppcollisions at the LHC using the ATLAS detector

“…The full GMSB SPS8 SUSY mass spectra, branching fractions and decay widths are calculated from this set of parameters using ISAJET [36] version 7.80. The HERWIG++ generator, version 2.4.2 [37], was used to generate the signal MC samples, with MRST 2007 LO* [38] parton density distributions (PDF).…”