Light Scenario Research Articles

Directional persistence of low wind speed observations

Low wind speed data is presented for stable, high-pressure sunny weather for an urban environment in the UK. In these climatologies, ventilation of buildings and dispersal of pollutants is often considered inadequate. Persistence, the length of time in which the wind blows in a specific direction and for a given angular range, is analysed. The observational data shows that in these low wind speed conditions, the wind blows in a consistent direction, for significant periods of time, and that truly calm conditions are very infrequent. The analysis of data for hot, dry, sunny and high-pressure conditions at one UK urban site, indicates that there are larger than expected air movements in these light wind scenarios. Values for mean duration of persistent wind episodes commonly exceed 30s, with similar values for the standard deviations. The Weibull statistical structure equally applies to these low wind speed observations. In this urban environment, for 45% of the time, the persistent wind events last longer than one standard deviation above the mean. At wind speeds lower than 2ms−1, the duration of persistent wind episodes remains constant and nor does it decrease with wind speed. This may be due to larger scale meteorological influences, perhaps convective activity and eddies in the boundary layer, which create air motions in calm daytime conditions in the UK.

Squark mixing in electron-positron reactions

Squark mixing plays a large role in the phenomenology of the minimal supersymmetric standard model, determining the mass of the lightest Higgs boson and the electroweak interactions of the squarks themselves. We examine how mixing may be investigated in high energy e + e reactions, both at LEP-II and the proposed linear collider. In particular, off-diagonal production of one lighter and one heavier squark allows one to measure the squark mixing angle, and would allow one to test the mass relations for the light Higgs boson. In some cases off-diagonal production may provide the best prospects to discover supersymmetry. In the context of the light bottom squark scenario, we show that existing data from LEP-II should show definitive evidence for the heavier �

SUDAKOV EXPANSIONS AT ONE-LOOP AND BEYOND FOR CHARGED SCALAR AND FERMION PAIR PRODUCTION IN SUSY MODELS AT FUTURE LINEAR COLLIDERS

We consider the high energy behavior of the amplitudes for pair production of charged leptons, quarks, Higgs bosons, sleptons, squarks and charginos at lepton colliders. We give the general expressions of the leading quadratic and subleading linear logarithms that appear at the one-loop level, and derive the corresponding resummed expansions to subleading logarithmic order accuracy. Under the assumption of a relatively light SUSY scenario and choosing the MSSM as a specific model, we compare the predictions of the one-loop and of the resummed expansions at variable energy. We show that the two predictions are very close in the one TeV regime, but drastically differ in the few (2,3) TeV range.

Charged Higgs boson production in the 1 TeV domain as a probe of the minimal supersymmetric standard model

We consider the production, at future lepton colliders, of charged Higgs pairs in supersymmetric models. Assuming a relatively light SUSY scenario, and working in the MSSM, we show that, for c.m. energies in the one TeV range, a one-loop logarithmic Sudakov expansion that includes an "effective" next-to subleading order term is adequate to the expected level of experimental accuracy. We consider then the coefficient of the linear (subleading) SUSY Sudakov logarithm and the SUSY next to subleading term of the expansion and show that their dependence on the supersymmetric parameters of the model is drastically different. In particular the coefficient of the SUSY logarithm is only dependent on $\tan\beta$ while the next to subleading term depends on a larger set of SUSY parameters. This would allow to extract from the data separate informations and tests of the model.

Double beta decay of Σ− hyperons

We compute the strangeness-conserving double beta decay of Σ− hyperons, which is the only hadronic system that can undergo such decays. We consider both, the lepton number conserving Σ−→Σ+e−e−ν̄ν̄ (ββΣ2ν) and the lepton number violating Σ−→Σ+e−e− (ββΣ0ν) modes. The branching ratios of these ββ decays are suppressed at the level of 10−30 considering a light neutrino scenario in the case of the ββΣ0ν channel. The dynamical origin of such low rates and their possible enhancements are briefly discussed. Given its simplicity those decays can be used also for the purposes of illustrating the main features of double beta decays.

Reliability of a high energy one-loop expansion of e+e−→ W+W− in the SM and in the MSSM

We compare the logarithmic Sudakov expansions of the process e + e −→ W + W − in the one-loop approximation and in the resummed version, to subleading order accuracy, in the SM case and in a light SUSY scenario for the MSSM. We show that the two expansions are essentially identical below 1 TeV, but differ drastically at higher (2, 3 TeV) center of mass energies. Starting from these conclusions, we argue that a complete one-loop calculation in the energy region below 1 TeV does not seem to need extra two-loop corrections, in spite of the relatively large size of the one-loop effects.

Signatures of the light scenario at the upgradedtevatron

In scenarios where gluinos and right-handed down-typesquarks are relatively light, motivated, for example, bytheSO(10) D terms, jets + signalscan be observed at the luminosity-upgraded Tevatron, evenif the remaining squarks are very heavy. Most spectacularsignals are expected if the right-handed down-typesquarks are lighter than the gluino. In the conventionalMSUGRA model with very heavy squarks and the gluino mass,consistent with the LEP bound, on the common gauginomass, practically no signal is expected in this channel.The possibility of distinguishing between variousSUGRA-motivated scenarios by exploiting the and the jet pT distributions, oppositesign dileptons + jets + events and clean trilepton signals have been discussed.

Majorana neutrinos and same-sign dilepton production at LHC and in rare meson decays

We discuss same-sign dilepton production mediated by Majorana neutrinos in high-energy proton-proton collisions $pp\ra \ell^+ \ell^{\prime +}X$ for $\ell,~ \ell^\prime = e,~ \mu,~ \tau$ at the LHC energy $\sqrt{s}=14$ TeV, and in the rare decays of $K$, $D$, $D_s$, and $B$ mesons of the type $M^{+}\ra M^{\prime -}\ell ^{+}\ell ^{\prime+}$. For the $pp$ reaction, assuming one heavy Majorana neutrino of mass $m_N$, we present discovery limits in the $(m_{N},|U_{\ell N}U_{\ell^\prime N}|)$ plane where $U_{\ell N}$ are the mixing parameters. Taking into account the present limits from low energy experiments, we show that at LHC for the nominal luminosity L=100 fb$^{-1}$ there is no room for observable same-sign dilepton signals. However, increasing the integrated luminosity by a factor 30, one will have sensitivity to heavy Majorana neutrinos up to a mass $m_N\leq 1.5$ TeV only in the dilepton channels $\mu\mu$ and $\mu \tau$, but other dilepton states will not be detectable due to the already existing strong constraints. We work out a large number of rare meson decays, both for the light and heavy Majorana neutrino scenarios, and argue that the present experimental bounds on the branching ratios are too weak to set reasonable limits on the effective Majorana masses.

Update of the search for supersymmetric particles in scenarios with gravitino LSP and sleptons NLSP

An update of the search for sleptons, neutralinos and charginos in the context of scenarios where the lightest supersymmetric particle is the gravitino and the next-to-lightest supersymmetric particle is a slepton, is presented, together with the update of the search for heavy stable charged particles in light gravitino scenarios and Minimal Supersymmetric Standard Models. Data collected in 1999 with the DELPHI detector at centre-of-mass energies around 192, 196, 200 and 202 GeV were analysed. No evidence for the production of these supersymmetric particles was found. Hence, new mass limits were derived at 95% confidence level.

Participatory democratization reconceived

Since the 1970s participatory democracy has been a catchword for genuine, popular or progressive democratization. Since then the general climate has changed in several respects. How is participatory democracy now being conceived and reconceived? To contextualize this question I first consider ongoing discussions of democracy and democratization generally, and then zero in on participatory democracy and its various current meanings. Participatory democracy is now usually thought of, rather than as wholesale system change, in partial reforms, particularly decentralization and politics of empowerment. I conclude by offering dark and light scenarios of the future significance of participatory democratization.

Higher twist contributions to R-hadron phenomenology in the light gluino scenario

The open light gluino window allows non-trivial higher twist gluino contributions to the proton wave function. Using a two-component model originally developed for charm hadroproduction, higher twist intrinsic gluino contributions to final state R-hadron formation are shown to enhance leading twist production in the forward $x_{F}$ region. We calculate R-hadron production at $p_{\rm{lab}}=800$ GeV in pp, pBe, and pCu interactions with light gluino masses of 1.2, 1.5, 3.5, and 5.0 GeV.

On the varying speed of light in a brane-induced FRW universe

We investigate a string/M theoretic realization of the varying speed of light scenario. We consider a 3+1 dimensional probe-brane universe in the background of a black hole in the bulk formed by a stack of branes, in the spirit of Kiritsis (hep-th/9906206). We generalize the dynamics of the system at hand by including rotation and Hubble damping of the bulk space-time and show that this may lead to a mechanism to stabilize the brane-universe and hence fix the speed of light at late times.

STOP SQUARK SEARCH AT TEVATRON IN THE LIGHT SLEPTON SCENARIO

In minimal-supergravity-based supersymmetry models the charged sleptons as well as the sneutrinos may be lighter than the squarks. In such a light slepton scenario search for the lighter stop squark has been investigated in the dilepton + missing pT[Formula: see text](≥ 1) channel at Tevatron. In this scenario semileptonic decay of the lighter stop squark has been considered via off-shell and on-shell charginos. In the latter case the chargino undergoes pure leptonic two-body decay. We observe that for some favorable region of the MSSM parameter space one can probe the lighter stop squark mass up to 140 GeV with few events in the present data set for which the luminosity is 110 pb -1. At the MI upgrade one is likely to end up with more events.

Development of the IPC as a search tool

The background to the current concerns about the future of the IPC is outlined. This highlights the rapid growth of the documentation, the increased use of electronic storage of documents, the availability of alternative search tools, and the technical developments in the fields searched. A first suggestion is to scrap the rule on ‘last place’ allocation of terms, and similar rules, all designed primarily to limit the extent of the paper files. Other suggestions include a number of approaches to improved indexing, e.g., global, deep or light indexing scenarios, as well as ‘multiple classification’. These suggestions are predicated upon the expected increased use of computer-held databases and document copies, and the gradual demise of paper files. The paper concludes by examining the ‘IPC dilemma’. Thus it is the only major international classification for patents. It is used by nearly 100 patent offices around the world, many of whom could not justify using any other system. It is also the basis for internal classification schemes e.g., at the European and Japanese Patent Offices. However it equally clearly needs major changes to make good use of modern, electronic storage and information retrieval methods. The author concludes that ‘if it is not rejuvenated, it will be marginalised’.

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Molecular dynamics simulations were carried out to investigate the adsorption of a low-energy C20 on a reconstructed silicon (001)-(\(\)) surface. The impact energies of the C20 fullerene range from 1 eV/atom to 5 eV/atom. After impacting, the C20 molecule is found to move along (011) direction and resides either in the trough or on the dimer at the end of our simulations. The lateral motion of C20 on the surface is dependent on its incident energy. Chemical bonds are formed between C20 and the surface. By the force field analysis, we show that the anisotropic molecule-surface interaction plays the leading role in the lateral motion of C20 as well as its preferable adsorption sites on the dimerized Si surface. These findings are consistent with experimental observations of C60 on Si (001) surface and small carbon clusters on solid surfaces.

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Promptly decaying lightest neutralinos and long-lived staus are searched for in the context of light gravitino scenarios. It is assumed that the stau is the next to lightest supersymmetric particle ...

Water Mist (Fine Spray) Fire Protection in Light Hazard Occupancies

The capability of impingement type water mist (fine spray) nozzles, with operating pres sures lower than 12 bar, was investigated in full-scale fire tests using light hazard scenar ios. In these tests, four prototype nozzles were evaluated; however, only one of the nozzles (Nozzle A) provided satisfactory protection. The results of the tests, with Nozzle A, are reported as an indication of the capabilities of impingement type water mist nozzles in light hazard occupancies. Nozzle A was typically operated at a flow rate of 15 Lpm and a pressure of 10 bar. The fire tests were conducted in a room 5.5 m x 5.5 m with openings to two adjacent rooms (and in one test, an opening to a corridor). The fuel packages used in the fire tests were: the residential fuel package of Underwriters Laboratories (UL), a living room fuel package, a bedroom fuel package, and a shielded heptane pool fire. The UL and the living room fuel packages were used in a room corner and along a wall between two nozzles. Gas temperature measurements indicated that Nozzle A provided acceptable protection in the fire tests of this study with a total water flow rate of 45 Lpm. Based on the results of this study and a review of previous work with water mist systems, recommendations for approval testing and installation standards have been made for light hazard scenarios. Language: en

Top quark analysis in the light gluino scenario

The Fermilab top quark analysis is heavily dependent on the assumption of standard model backgrounds only. In the light gluino scenario, the stop quarks lie near the top in mass and their decays can influence the resulting top quark mass by an amount that is not small relative to the currently quoted errors. Several slight anomalies in the top quark analysis find a natural explanation in the light gluino case.

Bubbles in the supersymmetric standard model

We compute the tunneling probability from the symmetric phase to the true vacuum, in the first-order electroweak phase transition of the MSSM, and the corresponding Higgs profiles along the bubble wall. We use the resummed two-loop temperature-dependent effective potential, and pay particular attention to the light stop scenario, where the phase transition can be sufficiently strongly first-order not to wipe off any previously generated baryon asymmetry. We compute the bubble parameters which are relevant for the baryogenesis mechanism: the wall thickness and Δβ. The two-loop corrections provide important enhancement effects, with respect to the one-loop results, in the amount of baryon asymmetry.