Prospects for Supersymmetry at LEP2

Working within the framework of the minimal supergravity model with gauge coupling unification and radiative electroweak symmetry breaking (SUGRA), we map out regions of parameter space explorable by experiments at LEP2, for center of mass energy options of $\sqrt{s}=150,\ 175$, $190$ and 205 GeV. We compute signals from all accessible $2 \rightarrow 2$ SUSY pair production processes using the ISAJET simulation program, and devise cuts that enhance the signal relative to Standard Model backgrounds, and which also serve to differentiate various supersymmetric processes from one another. We delineate regions of SUGRA parameter space where production of neutralino pairs, chargino pairs, slepton pairs and the production of the light Higgs scalar of SUSY is detectable above Standard Model backgrounds and distinguishable from other SUSY processes. In addition, we find small regions of SUGRA parameter space where \te\te, \tz_2\tz_2 and \tnu_L\tnu_L production yields spectacular events with up to four isolated leptons. The combined regions of parameter space explorable by LEP2 are compared with the reach of Tevatron Main Injector era experiments. Finally, we comment on how the reach via the neutralino pair channel is altered when the radiative electroweak symmetry breaking constraint is relaxed.Comment: 22 page REVTEX file + 9 uuencoded figures; a uuencoded PS file with PS figures is available via anonymous ftp at ftp://hep.fsu.edu/preprints/baer/FSUHEP950501.u

Equilibrium valleys in spin glasses at low temperature

We investigate the 3-dimensional Edwards-Anderson spin glass model at low temperature on simple cubic lattices of sizes up to L=12. Our findings show a strong continuity among T>0 physical features and those found previously at T=0, leading to a scenario with emerging mean field like characteristics that are enhanced in the large volume limit. For instance, the picture of space filling sponges seems to survive in the large volume limit at T>0, while entropic effects play a crucial role in determining the free-energy degeneracy of our finite volume states. All of our analysis is applied to equilibrium configurations obtained by a parallel tempering on 512 different disorder realizations. First, we consider the spatial properties of the sites where pairs of independent spin configurations differ and we introduce a modified spin overlap distribution which exhibits a non-trivial limit for large L. Second, after removing the Z_2 (+-1) symmetry, we cluster spin configurations into valleys. On average these valleys have free-energy differences of O(1), but a difference in the (extensive) internal energy that grows significantly with L; there is thus a large interplay between energy and entropy fluctuations. We also find that valleys typically differ by sponge-like space filling clusters, just as found previously for low-energy system-size excitations above the ground state.Comment: 10 pages, 8 figures, RevTeX format. Clarifications and additional reference

SIGNALS FOR MINIMAL SUPERGRAVITY AT THE CERN LARGE HADRON COLLIDER: MULTI-JET PLUS MISSING ENERGY CHANNEL,

We use ISAJET to perform a detailed study of the missing transverse energy \eslt plus multi-jet signal expected from superparticle production at the CERN LHC. Our analysis is performed within the framework of the minimal supergravity model with gauge coupling unification and radiative electroweak symmetry breaking. We delineate the region of parameter space where the \eslt supersymmetry signal should be observable at the LHC and compare it to the regions explorable via searches for sleptons and for chargino/neutralino production. We confirm that, given a data sample of 10~\fb^{-1}, $m_{\tg}\sim 1300$ GeV can be explored if m_{\tq}\gg m_{\tg}, while $m_{\tg}\sim 2000$ GeV can be probed if m_{\tq}\simeq m_{\tg}. We further examine what information can be gleaned from scrutinizing this event sample. For instance, the multi-jet multiplicity yields information on whether squark production makes a significant contribution to the observed \eslt sample. Furthermore, reconstructing hemispheric masses may yield a measure of $m_{\tg}$ to $\sim 15-25\%$. Finally, for favourable ranges of parameters, by reconstructing masses of tagged $b\bar{b}$ jet pairs, it may be possible to detect Higgs bosons produced via sparticle cascade decay chains.Comment: 22 pages (REVTEX); a PS text file (etmiss.ps) and 12 figures (etlhc.uu or etlhc.ps) can be obtained via anonymous ftp at ftp://hep.fsu.edu/anonymous.bae

From Phineas Gage and Monsieur Leborgne to H.M.: Revisiting Disconnection Syndromes

On the 50th anniversary of Norman Geschwind's seminal paper entitled 'Disconnexion syndrome in animal and man', we pay tribute to his ideas by applying contemporary tractographymethods to understand whitematter disconnection in 3 classic cases that made history in behavioral neurology.We first documented the locus and extent of the brain lesion from the computerized tomography of Phineas Gage's skull and themagnetic resonance images of Louis Victor Leborgne's brain, Broca's first patient, and Henry Gustave Molaison. We then applied the reconstructed lesions to an atlas of white matter connections obtained from diffusion tractography of 129 healthy adults. Our results showed that in all 3 patients, disruption extended to connections projecting to areas distant from the lesion.We confirmed that the damaged tracts link areas that in contemporary neuroscience are considered functionally engaged for tasks related to emotion and decision-making (Gage), language production (Leborgne), and declarative memory (Molaison). Our findings suggest that even historic cases should be reappraised within a disconnection framework whose principles were plainly established by the associationist schools in the last 2 centuries

Social Interactions vs Revisions, What is important for Promotion in Wikipedia?

In epistemic community, people are said to be selected on their knowledge contribution to the project (articles, codes, etc.) However, the socialization process is an important factor for inclusion, sustainability as a contributor, and promotion. Finally, what does matter to be promoted? being a good contributor? being a good animator? knowing the boss? We explore this question looking at the process of election for administrator in the English Wikipedia community. We modeled the candidates according to their revisions and/or social attributes. These attributes are used to construct a predictive model of promotion success, based on the candidates's past behavior, computed thanks to a random forest algorithm. Our model combining knowledge contribution variables and social networking variables successfully explain 78% of the results which is better than the former models. It also helps to refine the criterion for election. If the number of knowledge contributions is the most important element, social interactions come close second to explain the election. But being connected with the future peers (the admins) can make the difference between success and failure, making this epistemic community a very social community too

Hypercharge and the Cosmological Baryon Asymmetry

Stringent bounds on baryon and lepton number violating interactions have been derived from the requirement that such interactions, together with electroweak instantons, do not destroy a cosmological baryon asymmetry produced at an extremely high temperature in the big bang. While these bounds apply in specific models, we find that they are generically evaded. In particular, the only requirement for a theory to avoid these bounds is that it contain charged particles which, during a certain cosmological epoch, carry a non-zero hypercharge asymmetry. Hypercharge neutrality of the universe then dictates that the remaining particles must carry a compensating hypercharge density, which is necessarily shared amongst them so as to give a baryon asymmetry. Hence the generation of a hypercharge density in a sector of the theory forces the universe to have a baryon asymmetry.Comment: 12 pages plus 1 Postscript figure available upon request. LBL 3482

A List Referring Monte Carlo Method for Lattice Glass Models

We present an effcient Monte-Carlo method for lattice glass models which are characterized by hard constraint conditions. The basic idea of the method is similar to that of the $N$-fold way method. By using a list of sites into which we can insert a particle, we avoid trying a useless transition which is forbidden by the constraint conditions. We applied the present method to a lattice glass model proposed by Biroli and M{\'e}zard. We first evaluated the efficiency of the method through measurements of the autocorrelation function of particle configurations. As a result, we found that the efficiency is much higher than that of the standard Monte-Carlo method. We also compared the efficiency of the present method with that of the $N$-fold way method in detail. We next examined how the efficiency of extended ensemble methods such as the replica exchange method and the Wang-Landau method is inflnuenced by the choice of the local update method. The results show that the efficiency is considerably improved by the use of efficient local update methods. For example, when the number of sites $N_{\rm site}$ is 1024, the ergodic time $\tau_{\rm E}$ of the replica exchange method in the grand-canonical ensemble, which is the average round-trip time of a replica in chemical-potential space, with the present local update method is more than $10^2$ times shorter than that with the standard local update method. This result shows that the efficient local update method is quite important to make extended ensemble methods more effective.Comment: 16 pages, 21 figures; 1 subsection, 1 appendix, and 5 figures are added, abstract is changed, 1 figure is remove

A frameshift mutation of the chloroplast matK coding region is associated with chlorophyll deficiency in the Cryptomeria japonica virescent mutant Wogon-Sugi

Wogon-Sugi has been reported as a cytoplasmically inherited virescent mutant selected from a horticultural variety of Cryptomeria japonica. Although previous studies of plastid structure and inheritance indicated that at least some mutations are encoded by the chloroplast genome, the causative gene responsible for the primary chlorophyll deficiency in Wogon-Sugi, has not been identified. In this study, we identified this gene by genomic sequencing of chloroplast DNA and genetic analysis. Chloroplast DNA sequencing of 16 wild-type and 16 Wogon-Sugi plants showed a 19-bp insertional sequence in the matK coding region in the Wogon-Sugi. This insertion disrupted the matK reading frame. Although an indel mutation in the ycf1 and ycf2 coding region was detected in Wogon-Sugi, sequence variations similar to that of Wogon-Sugi were also detected in several wild-type lines, and they maintained the reading frame. Genetic analysis of the 19 bp insertional mutation in the matK coding region showed that it was found only in the chlorophyll-deficient sector of 125 full-sibling seedlings. Therefore, the 19-bp insertion in the matK coding region is the most likely candidate at present for a mutation underlying the Wogon-Sugi phenotype