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Search Results: 1 - 10 of 219509 matches for " C. Ghag "
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The LUX direct dark matter search experiment
Chamkaur Ghag
Physics , 2014,
Abstract: The Large Underground Xenon (LUX) experiment completed its first physics run in 2013, taking 85.3 live-days of WIMP-search data, and produced the world's most stringent constraints on spin-independent scattering of Weakly Interacting Massive Particles (WIMPs) to date. A profile-likelihood analysis technique shows the data to be consistent with the background-only hypothesis. The LUX data are in strong disagreement with low-mass WIMP signal interpretations of the results from several recent direct detection experiments.
A New Analysis Method for WIMP searches with Dual-Phase Liquid Xe TPCs
K. Arisaka,P. Beltrame,C. Ghag,K. Lung,P. R. Scovell
Physics , 2012, DOI: 10.1016/j.astropartphys.2012.07.003
Abstract: A new data analysis method based on physical observables for WIMP dark matter searches with noble liquid Xe dual-phase TPCs is presented. Traditionally, the nuclear recoil energy from a scatter in the liquid target has been estimated by means of the initial prompt scintillation light (S1) produced at the interaction vertex. The ionization charge (C2), or its secondary scintillation (S2), is combined with the primary scintillation in Log(S2/S1) vs. S1 only as a discrimination parameter against electron recoil background. Arguments in favor of C2 as the more reliable nuclear recoil energy estimator than S1 are presented. The new phase space of Log(S1/C2) vs. C2 is introduced as more efficient for nuclear recoil acceptance and exhibiting superior energy resolution. This is achieved without compromising the discrimination power of the LXe TPC, nor its 3D event reconstruction and fiducialization capability, as is the case for analyses that exploit only the ionization channel. Finally, the concept of two independent energy estimators for background rejection is presented: E2 as the primary (based on C2) and E1 as the secondary (based on S1). Log(E1/E2) vs. E2 is shown to be the most appropriate phase space in which to evaluate WIMP signal candidates.
Expected Sensitivity to Galactic/Solar Axions and Bosonic Super-WIMPs based on the Axio-electric Effect in Liquid Xenon Dark Matter Detectors
K. Arisaka,P. Beltrame,C. Ghag,J. Kaidi,K. Lung,A. Lyashenko,R. D. Peccei,P. Smith,K. Ye
Physics , 2012, DOI: 10.1016/j.astropartphys.2012.12.009
Abstract: We present systematic case studies to investigate the sensitivity of axion searches by liquid xenon detectors, using the axio-electric effect (analogue of the photoelectric effect) on xenon atoms. Liquid xenon is widely considered to be one of the best target media for detection of WIMPs (Weakly Interacting Massive Particles which may form the galactic dark matter) using nuclear recoils. Since these detectors also provide an extremely low radioactivity environment for electron recoils, very weakly-interacting low-mass particles (< 100 keV/c^2), such as the hypothetical axion, could be detected as well - in this case using the axio-electric effect. Future ton-scale liquid Xe detectors will be limited in sensitivity only by irreducible neutrino background (pp-chain solar neutrino and the double beta decay of 136Xe) in the mass range between 1 and 100 keV/c^2. Assuming one ton-year of exposure, galactic axions (as non-relativistic dark matter) could be detected if the axio-electric coupling g_Ae is greater than 10^-14 at 1 keV/c^2 (or $10^-13 at 100 keV/c^2). Below a few keV/c^2, and independent of the mass, a solar axion search would be sensitive to a coupling g_Ae ~ 10^-12. This limit will set a stringent upper bound on axion mass for the DFSV and KSVZ models for the mass ranges m_A < 0.1 eV/c^2 and < 10 eV/c^2, respectively. Vector-boson dark matter could also be detected for a coupling constant alpha'/alpha > 10^-33 (for mass 1 keV/c^2) or > 10^-27 (for mass 100 keV/c^2).
Dominance of Enterobacteria among Histamine-Producing Bacteria Isolated from Indian Mackerel  [PDF]
Meena Tembhurne, Anita Ghag, Hirekudel Sanathkumar, Binaya Bhusan Nayak
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.37072
Abstract:

Histamine fish poisoning (HFP) is a major illness occurring throughout the world due to the consumption of quality of deteriorated fish containing pre-formed histamine from bacterial activities. In the study reported here, the histamine-producing bacteria were isolated from the muscle, gills and the gut of 19 samples of Indian mackerel (Rastrelliger kanagurta) from Mumbai, India. The isolates from modified Niven’s medium (MNM) were confirmed for their ability to produce histamine by using 4 different pH-indicator media, followed by HPLC analyses. Out of 202 isolates, 63 isolates produced considerable amounts of histamine on at least 3 out of 4 media used in this study. The histamine formers were identified by biochemical tests followed by sequencing of their 16SrDNA gene, which showed that 89% of the isolates belonged to 13 different genera of the family Enterobacteriaceae. The non-enterobacterial histamine-producing bacteria belonged to the genera Staphylococcus, Alkaligenes, Shewanella and Psychrobacter.

Studies of a three-stage dark matter and neutrino observatory based on multi-ton combinations of liquid xenon and liquid argon detectors
K. Arisaka,P. Beltrame,C. W. Lam,P. F. Smith,C. Ghag,D. B. Cline,K. Lung,Y. Meng,E. Pantic,P. R. Scovell,A. Teymourian,H. Wang
Physics , 2011, DOI: 10.1016/j.astropartphys.2012.05.006
Abstract: We study a three stage dark matter and neutrino observatory based on multi-ton two-phase liquid Xe and Ar detectors with sufficiently low backgrounds to be sensitive to WIMP dark matter interaction cross sections down to 10E-47 cm^2, and to provide both identification and two independent measurements of the WIMP mass through the use of the two target elements in a 5:1 mass ratio, giving an expected similarity of event numbers. The same detection systems will also allow measurement of the pp solar neutrino spectrum, the neutrino flux and temperature from a Galactic supernova, and neutrinoless double beta decay of 136Xe to the lifetime level of 10E27 - 10E28 y corresponding to the Majorana mass predicted from current neutrino oscillation data. The proposed scheme would be operated in three stages G2, G3, G4, beginning with fiducial masses 1-ton Xe + 5-ton Ar (G2), progressing to 10-ton Xe + 50-ton Ar (G3) then, dependent on results and performance of the latter, expandable to 100-ton Xe + 500-ton Ar (G4). This method of scale-up offers the advantage of utilizing the Ar vessel and ancillary systems of one stage for the Xe detector of the succeeding stage, requiring only one new detector vessel at each stage. Simulations show the feasibility of reducing or rejecting all external and internal background levels to a level <1 events per year for each succeeding mass level, by utilizing an increasing outer thickness of target material as self-shielding. The system would, with increasing mass scale, become increasingly sensitive to annual signal modulation, the agreement of Xe and Ar results confirming the Galactic origin of the signal. Dark matter sensitivities for spin-dependent and inelastic interactions are also included, and we conclude with a discussion of possible further gains from the use of Xe/Ar mixtures.
Characterization of the Hamamatsu R11410-10 3-Inch Photomultiplier Tube for Liquid Xenon Dark Matter Direct Detection Experiments
K. Lung,K. Arisaka,A. Bargetzi,P. Beltrame,A. Cahill,T. Genma,C. Ghag,D. Gordon,J. Sainz,A. Teymourian,Y. Yoshizawa
Physics , 2012, DOI: 10.1016/j.nima.2012.08.052
Abstract: To satisfy the requirements of the next generation of dark matter detectors based on the dual phase TPC, Hamamatsu, in close collaboration with UCLA, has developed the R11410-10 photomultipler tube. In this work, we present the detailed tests performed on this device. High QE (>30%) accompanied by a low dark count rate (50 Hz at 0.3 PE) and high gain (10^7) with good single PE resolution have been observed. A comprehensive screening measurement campaign is ongoing while the manufacturer quotes a radioactivity of 20 mBq/PMT. These characteristics show the R11410-10 to be particularly suitable for the forthcoming zero background liquid xenon detectors.
Extraction and separation of U(VI) and Th(IV) from hydrobromic acid media using Cyanex-923 extractant
Ghag Snehal M.,Pawar Suresh D.
Journal of the Serbian Chemical Society , 2010, DOI: 10.2298/jsc090617118g
Abstract: A systematic study of the solvent extraction of uranium(VI) and thorium(IV) from hydrobromic acid media was performed using the neutral phosphine oxide extractant Cyanex-923 in toluene. These metal ions were found to be quantitatively extracted with Cyanex-923 in toluene in the acidity range 5x10-5-1x10-4 M and 5x10-5-5x10-3 M, respectively, and they are stripped from the organic phase with 7.0 M HClO4 and 2.0- 4.0 M HCl, respectively. The effect of the equilibrium period, diluents, diverse ions and stripping agent on the extraction of U(VI) and Th(IV) was studied. The stoichiometry of the extracted species of these metal ions was determined based on the slope analysis method. The extraction reactions proceed by solvation and their probable extracted species found in the organic phase were UO2Br2 2Cyanex-923 and ThBr4 2Cyanex-923. Based on these results, a sequential procedure for their separation from each other was developed.
Petunia Floral Defensins with Unique Prodomains as Novel Candidates for Development of Fusarium Wilt Resistance in Transgenic Banana Plants
Siddhesh B. Ghag, Upendra K. Singh Shekhawat, Thumballi R. Ganapathi
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039557
Abstract: Antimicrobial peptides are a potent group of defense active molecules that have been utilized in developing resistance against a multitude of plant pathogens. Floral defensins constitute a group of cysteine-rich peptides showing potent growth inhibition of pathogenic filamentous fungi especially Fusarium oxysporum in vitro. Full length genes coding for two Petunia floral defensins, PhDef1 and PhDef2 having unique C- terminal 31 and 27 amino acid long predicted prodomains, were overexpressed in transgenic banana plants using embryogenic cells as explants for Agrobacterium–mediated genetic transformation. High level constitutive expression of these defensins in elite banana cv. Rasthali led to significant resistance against infection of Fusarium oxysporum f. sp. cubense as shown by in vitro and ex vivo bioassay studies. Transgenic banana lines expressing either of the two defensins were clearly less chlorotic and had significantly less infestation and discoloration in the vital corm region of the plant as compared to untransformed controls. Transgenic banana plants expressing high level of full-length PhDef1 and PhDef2 were phenotypically normal and no stunting was observed. In conclusion, our results suggest that high-level constitutive expression of floral defensins having distinctive prodomains is an efficient strategy for development of fungal resistance in economically important fruit crops like banana.
Measurement of the Range Component Directional Signature in a DRIFT-II Detector using 252Cf Neutrons
S. Burgos,E. Daw,J. Forbes,C. Ghag,M. Gold,C. Hagemann,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. St. J. Murphy,G. G. Nicklin,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,D. P. Snowden-Ifft,N. J. C. Spooner,J. Turk,E. Tziaferi
Physics , 2008, DOI: 10.1016/j.nima.2008.11.147
Abstract: The DRIFT collaboration utilizes low pressure gaseous detectors to search for WIMP dark matter with directional signatures. A 252Cf neutron source was placed on each of the principal axes of a DRIFT detector in order to test its ability to measure directional signatures from the three components of very low energy (~keV/amu) recoil ranges. A high trigger threshold and the event selection procedure ensured that only sulfur recoils were analyzed. Sulfur recoils produced in the CS2 target gas by the 252Cf source closely match those expected from massive WIMP induced sulfur recoils. For each orientation of the source a directional signal from the range components was observed, indicating that the detector is directional along all 3 axes. An analysis of these results yields an optimal orientation for DRIFT detectors when searching for a directional signature from WIMPs. Additional energy dependent information is provided to aid in understanding this effect.
Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches
S. Burgos,E. Daw,J. Forbes,C. Ghag,M. Gold,C. Hagemann,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. St. J. Murphy,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,D. P. Snowden-Ifft,N. J. C. Spooner,J. Turk,E. Tziaferi
Physics , 2009, DOI: 10.1088/1748-0221/4/04/P04014
Abstract: Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches.
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