Constraining R-parity violating couplings using dimuon data at Tevatron Run-II

The dimuon plus dijet signal is analyzed in the top squark pair production at Tevatron Run-II experiment and the total event rate is compared with the existing dimuon data. This comparison rules out top squark mass upto 188(104) GeV for the branching fraction 100%(50%) of top squark decay into the muon plus quark via lepton number violating coupling. Interpretation of this limit in the framework of R-parity violating(RPV) SUSY model puts limit on relevant RPV coupling for a given top squark mass and other supersymmetric model parameters. If \MST \lsim 180 GeV we found that the RPV couplings are roughly restricted to be within $\sim 10^{-4}$ which is at the same ballpark value obtained from the neutrino data. The limits are very stringent for a scenario where top squarks appear to be the next lightest supersymmetric particles.Comment: 7 pages, 3 figures,added minor clarifications,version to appear in Phys. Lett.

Strategies to control invasion of Sailfin Armoured Catfish, Pterygoplichthys spp. in wastewater-fed aquaculture bheries of East Kolkata Wetland, India with suggestion of a modified barrier based on the biological and behavioural characteristics

Sailfin armoured catfish (Pterygoplichthys spp.), an alien invasive species of family Loricariidae has invaded extensively in wastewater-fed large aquaculture ponds (locally called ‘bheries’) of East Kolkata Wetlands (EKW), West Bengal, India. As there is no viable controlling method at present, commonly these fishes are removed by different physical methods and discarded. In the present study, we investigated the effectiveness and suitability of different in-practice Pterygoplichthys spp. control methods, based on on-field sampling, biological and behavioural study of the fish and also response analysis of the stakeholder’s of EKW. The results indicate that in-practice eradication efforts, like ‘repeated seine netting’ with or without removal of Eichhornia sheath of the pond periphery and ‘dewatering of pond’ aiming to reduce or eradicate Pterygoplichthys spp., are not fully effective, because of the capture avoidance ability and burrowing habit of these fishes. We found deep and branching burrows of Pterygoplichthys spp. in aquaculture ponds of EKW, with maximum burrow depth of 58 cm, and water in that burrows even after 12 days of dewatering. Hence, it is suggested stakeholders to keep dewatered pond exposed to sunlight for at least four weeks or above to ensure complete water-out from the burrows in which Pterygoplichthys spp. take shelter or lay their eggs. ‘Multilayer bamboo fencing’ or ‘combination of bamboo fencing and net barrier’ use by the stakeholders of EKW to prevent intrusion or re-intrusion of Pterygoplichthys spp. were found only partially effective, because of the capability of these fishes to damage net-blocking through their hard dorsal and pectoral spines or entry through the holes dug across the barrier in beneath or banks of the sewage intake channel. Based on learning on the biological and behavioural characteristics of Pterygoplichthys spp., we then suggested a modified version of barrier to the stakeholder’s of EKW, incorporating a sewage feeder pipeline, a concrete collection chamber with size separation arrangement made of hard materials like wire mesh and a dam of specific dimensions across the channel, for effective prevention of intrusion of these fishes in their aquaculture bheries

A RETROSPECTIVE STUDY ON THE INCIDENCE OF FISH DISEASES AND USE OF THERAPEUTANTS IN AQUACULTURE FARMS OF MOYNA, THE ‘FISHERIES HUB’ OF WEST BENGAL, INDIA

The present study depicts the disease incidences in the aqua farms of Moyna, West Bengal, India, during 2018- 2020 and aqua-drugs used by farmers to combat diseases. A total of 132 fish disease incidences were reported, among which parasitic diseases were the most common (53.03%) followed by bacterial diseases (27.27%), diseases due to poor nutrition and environmental fluctuations (10.61%), and fungal diseases (9.09%), respectively. Out of the 53.03% parasitic disease incidences reported, Argulus (22.86%), Dactylogyrus (17.14%), Gyrodactylus (10.00%), Myxospores (10.00%), Lernaea (8.57%), Ichthyophthirius (5.71%) and Trichodina (4.29%) were the major disease-causing parasites. Among bacteria, Pseudomonas spp. and Aeromonas spp. were the most dominant genera encountered in diseased fish. Labeo catla was the most susceptible fish species followed by Labeo rohita, and Cirrhinus mrigala. Seasonal influence in disease occurrence was noticed. Monsoon and winter were favorable seasons for disease outbreaks. The influence of water quality parameters like hardness, pH, ammonia, total dissolved solids of water, and total organic carbon of sediment had a significant correlation with parasite abundance. Farmers of Moyna were observed to use a wide range of chemicals and aqua-drugs to control diseases and related problems. The majority of the fish farms of Moyna were found using feed additives and supplements (32.00%) followed by sanitizers and disinfectants (24.00%), probiotics (17.00%), anti-parasitic drugs (11.00%), antibiotics (8.00%), and other chemicals (20.00%). Lime (calcium carbonate) and zeolite along with sodium chloride, potassium permanganate, formalin, and calcium hypochlorite were extensively used as disinfectants in Moyna. Farmers being unaware of the adverse consequences of using chemicals and aqua-medicines are fully dependent on private aquaculture consultants for time-to-time advice, which may have augmented their indiscriminate use. Initiative for the implementation of better management practices by creating awareness among farmers and adopting strict aquaculture policy guidelines might improve the scenario

Constraining top squark in R-parity violating SUSY model using existing Tevatron data

Signal of lighter top squark has been looked for using Tevatron data in the di-electron plus di-jet channel. We find that the mass of the lighter top squark when it decays dominantly in the electron plus jet channel, can be ruled out up to 220 GeV at 95% C.L. using di-electron data. In the framework of R-parity breaking SUSY model we exclude relevant R-parity violating couplings for a range of top squark masses and other SUSY parameters. The bounds on R-parity violating couplings are very stringent for the parameter space where lighter top squark turns out to be the next to lightest supersymmetric particle.Comment: 12 pages, 4 Figures, LateX, minor changes, few references added, version to appear in Physical Rev.

Probing R-parity violating models of neutrino mass at the Tevatron via top Squark decays

We have estimated the limiting branching ratio of the R-parity violating (RPV) decay of the lighter top squark, \tilde t_1 \ar l^+ d ($l=e$ or $\mu$ and d is a down type quark of any flavor), as a function of top squark mass(\MST) for an observable signal in the di-lepton plus di-jet channel at the Tevatron RUN-II experiment with 2 fb$^{-1}$ luminosity. Our simulations indicate that the lepton number violating nature of the underlying decay dynamics can be confirmed via the reconstruction of \MST. The above decay is interesting in the context of RPV models of neutrino mass where the RPV couplings ($\lambda'_{i3j}$) driving the above decay are constrained to be small (\lsim 10^{-3} - 10^{-4} ). If $\tilde t_1$ is the next lightest super particle - a theoretically well motivated scenario - then the RPV decay can naturally compete with the R-parity conserving (RPC) modes which also have suppressed widths. The model independent limiting BR can delineate the parameter space in specific supersymmetric models, where the dominating RPV decay is observable and predict the minimum magnitude of the RPV coupling that will be sensitive to Run-II data. We have found it to be in the same ballpark value required by models of neutrino mass, for a wide range of \MST. A comprehensive future strategy for linking top squark decays with models of neutrino mass is sketched.Comment: 28 pages, 14 Figure

Summary of the Activities of the Working Group I on High Energy and Collider Physics

This is a summary of the projects undertaken by the Working Group I on High Energy Collider Physics at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai, January 5-16, 2004. The topics covered are (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider.Comment: summary of Working Group I at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8), I.I.T., Mumbai, January 5-16, 200

Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron

The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of $\sqrt s =1.96$ TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is $A_{\mathrm{FB}}^{t\bar{t}} = 0.128 \pm 0.025$. The combined inclusive and differential asymmetries are consistent with recent standard model predictions