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Search Results: 1 - 10 of 27685 matches for " Diganta Kumar Das "
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Synthesis, Spectroscopy, Thermal Analysis, Electrochemistry and Superoxide Scavenging Activity of a New Bimetallic Copper(II) Complex
Babita Sarma,Diganta Kumar Das
Journal of Chemistry , 2013, DOI: 10.1155/2013/349580
Abstract:
HANDWRITING CHARACTERS RECOGNITION ERRORS AND RECOGNIZING ERRORS OF CHILDREN ON THE TABLET PC
Diganta Das
International Journal of Science, Environment and Technology , 2012,
Abstract:
HANDWRITING RECOGNITION RATE AND PREFERENCE OF WRITING
Diganta Das
International Journal of Science, Environment and Technology , 2012,
Abstract:
New Physics Effects and Hadronic Form Factor Uncertainties in B -> K^* l^+ l^-
Diganta Das,Rahul Sinha
Physics , 2012, DOI: 10.1103/PhysRevD.86.056006
Abstract: It is well known that New Physics can contribute to weak decays of heavy mesons via virtual processes during its decays. The discovery of New Physics, using such decays is made difficult due to intractable strong interaction effects needed to describe it. Modes such as B -> K^* l^+ l^- offer an advantage as they provide a multitude of observables via angular analysis. We show how the multitude of "related observables" obtained from B -> K^* l^+ l^-, can provide many new "clean tests" of the Standard Model. The hallmark of these tests is that several of them are independent of the unknown universal form factors in heavy quark effective theory. We derive a relation between observables that is free of form factors and Wilson coefficients, the violation of which will be an unambiguous signal of New Physics. We also derive relations between observables and form factors that are independent of Wilson coefficients and enable verification of hadronic estimates. We show how form factor ratios can be measured directly from helicity fraction with out any assumptions what so ever. We find that the allowed parameter space for observables is very tightly constrained in Standard Model, thereby providing clean signals of New Physics. We examine both the large-recoil and low-recoil regions of the K^* meson and point out special features and derive relations between observables valid in the two limits. In the large-recoil regions several of the relations are unaffected by corrections to all orders in \alpha_s. We present yet another new relation involving only observables that would verify the validity of the relations between form-factors assumed in the low-recoil region. The several relations and constraints derived will provide unambiguous signals of New Physics if it contributes to these decays.
Isolating New Physics Effects from Hadronic Form Factor Uncertainties in B\to K^* \ell^+\ell^-
Diganta Das,Rahul Sinha
Physics , 2012,
Abstract: The discovery of New Physics, using weak decays of mesons is difficult due to intractable strong interaction effects needed to describe it. We show how the multitude of "related observables" obtained from B\to K^* \ell^+\ell^-, can provide many new "clean tests" of the Standard Model. The hallmark of these tests is that several of them are independent of the unknown form factors required to describe the decay using heavy quark effective theory. We derive a relation between observables that is free of form factors and Wilson coefficients, the violation of which will be an unambiguous signal of New Physics. We also derive other relations between observables and form factors that are independent of Wilson coefficients and enable verification of hadronic estimates. We find that the allowed parameter space for observables is very tightly constrained in Standard Model, thereby providing clean signals of New Physics. The relations derived will provide unambiguous signals of New Physics if it contributes to these decays.
B->Kπll in and outside the K* window
Diganta Das,Gudrun Hiller,Martin Jung
Physics , 2015,
Abstract: We study the impact of B->Kpill decays on B->K*(->Kpi)ll, taking into account the K* at finite width. Interference effects can generically be sizable, up to O(10%), but are reduced in several ratios of observables of the angular distribution. Information on strong phases is central to control interference effects, which cannot be removed by sideband subtractions. We point out ways to probe the strong phases; only a single one is required to describe leading effects in the region of low hadronic recoil. We find that recent LHCb data on the B0->K*0mumu angular observables at low recoil are in good agreement with the standard model.
Testing New Physics Effects in $B \to K^*\ell^+\ell^-$
Rusa Mandal,Rahul Sinha,Diganta Das
Physics , 2014, DOI: 10.1103/PhysRevD.90.096006
Abstract: It is generally believed that the decay mode $B\to K^*\ell^+\ell^-$ is one of the best modes to search for physics beyond the standard model. The angular distribution enables the independent measurement of several observables as a function of the dilepton invariant mass. The plethora of observables so obtained enable unique tests of the standard model contributions. We start by writing the most general parametric form of the standard model amplitude for $B\to K^*\ell^+\ell^-$ taking into account comprehensively all contributions within SM. These include all short-distance and long-distance effects, factorizable and non-factorizable contributions, complete electromagnetic corrections to hadronic operators up to all orders, resonance contributions and the finite lepton and quark masses. The parametric form of the amplitude in the standard model results a new relation involving all the $CP$ conserving observables. The derivation of this relation only needs the parametric form of the amplitude and not a detailed calculation of it. Hence, we make no approximations, however, innocuous. The violation of this relation will provide a smoking gun signal of new physics. We use the $1 \text{fb}^{-1}$ LHC$b$ data to explicitly show how our relation can be used to test standard model and search for new physics that might contribute to this decay.
INDIGENOUS PEOPLE’S DISPLACEMENT TO THE URBAN AREAS AND ITS EFFECTS: A CASE STUDY
DIGANTA KUMAR PHUKAN, NABA KRISHNA BORAH
International Journal for Basic Sciences and Social Sciences , 2012,
Abstract: Displacement is one of the causes for migration of indigenous people to urban areas. This study was conducted among the Mising people of North Lakhimpur Town, the Headquarter of the Lakhimpur District, Assam, who have migrated as a result of displacement due to heavy riverbank erosion and flood. The study depicted that they are having problem in case of food, shelter, dress, education, health and gradually the traditional culture is eroded among them and all these stand as the great challenge in front of them.
A Multisensor Analysis of the Life Cycle of Bow Echo over Indian Region
Devajyoti Dutta,Diganta Kumar Sarma,Sanjay Sharma
International Journal of Atmospheric Sciences , 2014, DOI: 10.1155/2014/207064
Abstract: This study deals with the life cycle of bow echo events on October 24 and 26-27, 2006, from Doppler weather radar (DWR) observations supported by Radiosonde and National Centers for Environmental Prediction (NCEP). The cell bow echo (CBE) on October 24 evolved from two small isolated cells with radar reflectivity ≥40?dBZ. The vertical structure consists of one single mature cell with 20?dBZ echoes reaching up to 10?km while 40?dBZ echoes extended uniformly from ground to ~5?km height. The radial velocity shows a high value >?15?m/s towards the radar at the upper height (about 6 to 11?km); the lower height is predominant with velocity away from the radar (about 5 to 15?m/s). The squall line bow echo on October 26 and 27 has its origin over ocean and moved towards the radar site and decayed thereafter. The radar reflectivity pattern for this squall line showed it to be a trailing stratiform type squall line with length of ~200?km. The echo top height was more than 12?km in height. Strong inflow cases were observed from both radiosonde and radar. 1. Introduction The life cycle of mesoscale convective systems (MCSs) can be studied with the help of on-board IR and microwave sensors as well as ground based Doppler weather radar (DWR) [1]. Though the geostationary IR data is very useful for the study of evolution of MCSs because of its large areal coverage, it can give only the cloud top information but unable to give details inside of the system. On the other hand, DWR can give much better information of the MCS but their coverage is limited, where the reliable observation >200?km is restricted due to the refraction of the transmitted signal. The passive microwave radiometer cannot be used for the study of the evolution of MCSs as these are carried by polar satellite with low repetition. A multisensor approach is useful approach to study the multifaceted characteristics of MCSs. Till date many of the studies of MCSs are performed with the help of both active and passive sensors: evolution (e.g., [2–6]), size and structure [7, 8], and reflectivity structures (e.g., [9–12]). The severe weather events are mostly associated with the organized MCSs such as bow echoes and squall lines. Bow echoes were named and described in detail by Fujita [13]. A bow echo is defined as a nontransient bow or crescent shaped radar signature with a high reflectivity gradient on the convex edge. Most of the time, they are associated with severe weather. According to Fujita [13] the bow echo commonly evolves from either a single convective cell or a line of cells. Klimowsky et al.
Assessing Consistency of Consumer Confidence Data using Dynamic Latent Class Analysis
Sunil Kumar,Zakir Husain,Diganta Mukherjee
Quantitative Finance , 2015,
Abstract: In many countries information on expectations collected through consumer confidence surveys are used in macroeconomic policy formulation. Unfortunately, before doing so, the consistency of responses is often not taken into account, leading to biases creeping in and affecting the reliability of the indices hence created. This paper describes how latent class analysis may be used to check the consistency of responses and ensure a parsimonious questionnaire. In particular, we examine how temporal changes may be incorporated into the model. Our methodology is illustrated using three rounds of Consumer Confidence Survey (CCS) conducted by Reserve Bank of India (RBI).
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