Virtual LSPs at e+ e− colliders

Currently popular search strategies for supersymmetric particles may be significantly affected due to relatively light sneutrinos which decay dominantly into invisible channels. In certain cases the second lightest neutralino may also decay invisibly leading to two extra carriers of missing energy (in addition to the lightest supersymmetric particle (LSP) ) — the virtual LSPs (VLSPs). A tree lavel calculation shows that if the sneutrino mass happens to be in the small but experimentally allowed range (m _≈ν ≈ 45–55 GeV), these particles together with neutralino pairs may contribute significantly to the missing energy in the process e⁺e^? → γ+ E at LEP-2 energies as an enhancement over the Standard Model or the conventional MSSM predictions. It is further shown that a much larger region of the parameter space can be scanned at a high luminosity e⁺e^? collider at 500 GeV like the proposed NLC machine. Moreover, at both LEP-2 and NLC this process may play a complementary role to direct chargino searches, which may fail due to a near mass degeneracy of the chargino and the sneutrino. Formulae for the cross sections taking into account full mixings of the charginos and the neutralinos are derived. The signal remains observable even in the context of more restricted models based onN=1 SUGRA with common scalar and gaugino masses. A preliminary study of the QED radiative corrections due to soft multiple photon emission as well as hard collinear bremsstrahlung indicates that these corrections play a crucial role in estimating the background.     

Working group report: Neutrino and astroparticle physics

This is the report of neutrino and astroparticle physics working group at WHEPP-7. Discussions and work on CP violation in long baseline neutrino experiments, ultra high energy neutrinos, supernova neutrinos and water Cerenkov detectors are discussed.     

超导纳米线单光子探测器件的制备

超导纳米线单光子探测器件(SNSPD)是超导单光子探测系统的核心器件。文中介绍了成功制备的基于5nm厚的NbN超导超薄薄膜的SNSPD器件。器件核心结构为150nm宽的纳米曲折线结构,纳米线条占空比为75%,面积为20μm×20μm。超导纳米线是利用电子束曝光(EBL)技术和反应离子刻蚀(RIE)等工艺技术制备的。所制备的SNSPD样品,在温度3.5K下的临界电流约12.9μA;在1310nm波长光波辐照,12.5μA的偏置电流下,探测效率约0.016%。     

Super Kobayashi-Maskawa CP-violation

We argue that in the minimal SUSY extension of the standard model, CP-violation cannot be explained through SUSY phase alone. But SUSY graphs, especially with gluinos, can make important contributions to CP-violation through the Kobayashi-Maskawa phase.     

Effect of water and air-water interface on the structural modification of Ni-arachidate Langmuir-Blodgett films

Nickel arachidate (NiA) Langmuir-Blodgett (LB) films have been deposited on hydrophilic Si(0 0 1) substrates by three (up-down-up) and five (up-down-up-down-up) strokes. During deposition, substrates were kept inside the water subphase for different times after each down stroke. Structural information of all the LB films have been obtained from X-ray reflectivity (XRR) studies. One and two symmetric monolayer (SML) was deposited on top of the asymmetric monolayer (AML) in three and five stokes respectively. All the preformed LB films were then used to go through the air-water interface with the same speed that was used at the time of film deposition. Structural information obtained from the XRR studies show that mainly the top layer density decreases after passing through the air-water interface but the layered structure remains the same. Information obtained from both the XRR and atomic force microscopy (AFM) studies suggest that molecules peeled from the top SML layer do not reincorporate with the LB film through tail-tail hydrophobic interaction. Our study shows that NiA LB film has better stability compared with cadmium arachidate LB film inside the water subphase without forming any out-of-plane molecular reorganization.     

High-Temperature superconductivity in the Y–Ba–Cu–O system

High-temperature superconductivity in the Y-Ba-Cu-O system has been discussed with special reference to the identification and characterization of the pure monophasic compound responsible for the superconductivity. The crucial role of oxygen has been examined in the light of the structure and thermogravimetric analysis.     

Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

A new three-flavor oscillation solution of the solar neutrino deficit in <Emphasis Type="Italic">R</Emphasis>-parity violating supersymmetry

We present a solution of the solar neutrino deficit using three flavors of neutrinos and R-parity non-conserving supersymmetry. In this model, in vacuum, the is massless and unmixed, mass and mixing being restricted to the - sector only, which we choose in consistency with the requirements of the atmospheric neutrino anomaly. The flavor changing and flavor diagonal neutral currents present in the model and the three-flavor picture together produce an energy dependent resonance-induced - mixing in the sun. This mixing plays a key role in the new solution to the solar neutrino problem. The best fit to the solar neutrino rates and spectrum (1258-day SK and 241-day SNO data) requires a mass square difference of eV² in vacuum between the two lightest neutrinos. This solution cannot accommodate a significant day-night effect for solar neutrinos nor CP violation in terrestrial neutrino experiments. Received: 26 December 2001 / Revised version: 16 February 2002 / Published online: 26 July 2002     

Singlet-Higgs-Boson signals at hadron colliders

Many extensions of the Standard Model includeSU(2) _L ×U(1) _Y singlet higgs bosons,h ⁰, and also vector-like fermions which couple to it. The production and detection possibilities of such singlet neutral scalars at hadron colliders are considered for different scenarios of vectorlike fermions. We find that for some values of masses and couplings, detection at the CERN large hadron collider (LHC) appears to be a distinct possibility, while at the Fermilab Tevatron upgrade theh ⁰ might be observed only in very favourable circumstances.     

Dual interpretation of electromagnetic fields in general relativity

An energy stress tensor satisfying Rainich's algebraic relations along with a specified metric tensor sometimes admits two alternative Maxwell fields-one with a nonvanishing current vector as source and the other without any source. This paper investigates the conditions for the existence of a source-free interpretation when a with source solution with various types of the source current vector (i.e., timelike, null, or spacelike) is known and illustrates the results with some examples. It turns out that in the case of timelike currents, a dual interpretation requires this to be a purely convection current, while in other cases a dual interpretation is possible only if the conductivity is infinite and the conduction current is in the direction of the magnetic field.