Can the Aleph four-jet excess be explained in a supersymmetric model with R-parity violation?

We investigate the possibility that the excess of four-jet events in e ⁺ e ^? collisions at LEP-1.5 which has been reported by the ALEPH Collaboration could be due to the production of charginos or neutralinos, followed by their decay into quark jets through baryon number-violating (λ″) couplings. An estimate at the parton level shows, however, that these events cannot be due to neutralinos because of the low cross-section, and is unlikely to be due to the production of chargino pairs because of the largely different event shapes.     

Resolved photon processes

After giving a very brief introduction to the resolved photon processes, I will summarize the latest experimental information from HERA, on resolved photon contribution to largep _T jet production as well as to direct photon production. I will point out the interesting role that resolved photon processes can play in increasing our understanding of the dynamics of the quarkonium production. I will then discuss the newer information on the parton content of virtual photons as well as thek _T distribution of the partons in the photon. I will end by giving predictions of an eikonalized minijet model for σ _γγ ^inel which crucially uses the experimental measurement of the abovementionedk _T distribution and comparing them with data. On leave of absence from Department of Physics, University of Bombay, Mumbai 400 076, India     

Resolved photon processes

We review high-energy scattering processes that are sensitive to the hadronic structure of the photon, describing theoretical predictions as well as recent experimental results. These processes include deep-inelastic electron-photon scattering ate ⁺ e ⁻ colliders; and the production of jets, heavy quarks and isolated photons in the collision of real photons ate ⁺ e ⁻ colliders, as well as in photon-photon collisions atep colliders. We also comment on minijet based calculations of totalγp andγγ cross-sections, and discuss the possibility that future lineare ⁺ e ⁻ colliders might produce very large photon fluxes due to the beamstrahlung phenomenon; in the most extreme cases, we predict more than one hadronicγγ event to occur at every bunch crossing.     

A lab-on-chip for biothreat detection using single-molecule DNA mapping

Rapid, specific, and sensitive detection of airborne bacteria, viruses, and toxins is critical for biodefense, yet the diverse nature of the threats poses a challenge for integrated surveillance, as each class of pathogens typically requires different detection strategies. Here, we present a laboratory-on-a-chip microfluidic device (LOC-DLA) that integrates two unique assays for the detection of airborne pathogens: direct linear analysis (DLA) with unsurpassed specificity for bacterial threats and Digital DNA for toxins and viruses. The LOC-DLA device also prepares samples for analysis, incorporating upstream functions for concentrating and fractionating DNA. Both DLA and Digital DNA assays are single molecule detection technologies, therefore the assay sensitivities depend on the throughput of individual molecules. The microfluidic device and its accompanying operation protocols have been heavily optimized to maximize throughput and minimize the loss of analyzable DNA. We present here the design and operation of the LOC-DLA device, demonstrate multiplex detection of rare bacterial targets in the presence of 100-fold excess complex bacterial mixture, and demonstrate detection of picogram quantities of botulinum toxoid.     

Binary consecutive covering arrays

A k × n array with entries from a q-letter alphabet is called a t-covering array if each t × n submatrix contains amongst its columns each one of the q ^t different words of length t that can be produced by the q letters. In the present article we use a probabilistic approach based on an appropriate Markov chain embedding technique, to study a t-covering problem where, instead of looking at all possible t × n submatrices, we consider only submatrices of dimension t × n with its rows being consecutive rows of the original k × n array. Moreover, an exact formula is established for the probability distribution function of the random variable, which enumerates the number of deficient submatrices (i.e., submatrices with at least one missing word, amongst their columns), in the case of a k × n binary matrix (q = 2) obtained by realizing kn Bernoulli variables.     

CP violation in supersymmetry, Higgs sector and the large hadron collider

In this talk I discuss some aspects of CP violation (CPV) in supersymmetry (SUSY) as well as in the Higgs sector. Further, I discuss ways in which these may be probed at hadronic colliders. In particular I will point out the ways in which studies in the sector at the Tevatron may be used to provide information on this and how the search can be extended to the LHC. I will then follow this by a discussion of the CP mixing induced in the Higgs sector due to the above-mentioned CPV in the soft SUSY breaking parameters and its effects on the Higgs phenomenology at the LHC. I would then point out some interesting aspects of the phenomenology of a moderately light charged Higgs boson, consistent with the LEP constraints, in this scenario. Decay of such a charged Higgs boson would also allow a probe of a light (≲50 GeV), CP-violating (CPV) Higgs boson. Such a light neutral Higgs boson might have escaped detection at LEP and could also be missed at the LHC in the usual search channels.     

Variational wave-function study of the triangular lattice supersolid

We present a variational wave function which explains the behavior of the supersolid state formed by hard-core bosons on the triangular lattice. The wave function is a linear superposition of only and all configurations minimizing the repulsion between the bosons (which it thus implements as a hard constraint). Its properties can be evaluated exactly--in particular, the variational minimization of the energy yields (i) the surprising and initially controversial spontaneous density deviation from half-filling (ii) a quantitatively accurate estimate of the corresponding density wave (solid) order parameter.     

Quenching of photoconductivity in Fe doped CdS thin films prepared by spray pyrolysis technique

Fe doped CdS films are prepared using spray pyrolysis technique. All the samples are found to be of single phase and crystallized in hexagonal lattice. The X-ray diffraction peaks position of Cd_1−xFe_xS shifts to higher angle with increasing Fe concentration indicating decrease in cell volume. The temperature dependence of resistivity follows Arrhenius behavior having lower activation energy with increasing Fe concentration in dark while there is a little variation in light. Pure CdS films are having large photoconductivity. Upon Fe incorporation, this photoconductivity gradually decreases and for concentration more than 20%, it is almost vanished. Note worthy observation is the changes seen in morphology with AFM, viz. nanorod features seen in CdS is changed to continuous nanorod like structures depicting signatures of Ostwald ripening.