242 research outputs found
Heavy light tetraquarks from Lattice QCD
We present preliminary results from a lattice calculation of tetraquark
states in the charm and bottom sector of the type ,
, and . These
calculations are performed on MILC ensembles with lattice
spacing of and . A relativistic
action with overlap fermions is employed for the light and charm quarks while a
non-relativistic action with non-perturbatively improved coefficients is used
in the bottom sector. Preliminary results provide a clear indication of
presence of energy levels below the relevant thresholds of different tetraquark
states. While in double charm sector we find shallow bound levels, our results
suggest deeply bound levels with double bottom tetraquarks.Comment: Corrected threshold for the tetraquark state.
Proceedings of the 35th International Symposium on Lattice Field Theory,
18-24 June 2017, Granada, Spain. TIFR preprint no : TIFR/TH/17-3
Study of the effect of Bucillamine on the early and late phase of hepatic ischaemia reperfusion injury.
Ischaemia of the liver followed by reperfusion results in endothelial and
parenchymal injury through a complex cascade of events. This often occurs in
human liver transplantation as well as with major liver resections and is referred
to as Ischaemia Reperfusion (IR) Injury. Bucillamine is a low molecular weight
thiol antioxidant that is capable of rapidly entering cells.
This thesis evaluates the effect of Bucillamine on both the early and late phases
of liver warm IR injury with the hypothesis that beneficial effects are induced
could be due to its action as a free radical scavenger. The drug was evaluated in
an in vivo lobar liver ischemia reperfusion model as previously described. Male
Sprague –Dawley rats were subjected to 45 mins of partial hepatic (70 %)
ischaemia followed by 3 hrs of reperfusion to investigate the early phase of
hepatic IR and 24 hrs of reperfusion to study the late phase of hepatic IR.
Changes to the microcirculation, leucocyte adherence and apoptosis were
assessed by intra-vital microscopy. Hepatocellular injury was assessed by
standard liver function tests. Expression of pro and antiapoptotic gene
expression was studied by RT-PCR. Oxidative stress was assessed by
measuring plasma and hepatic F2 isoprostane levels and tissue glutathione
levels. Cytokine response was assessed by measuring serum CINC-1 levels.
Bucillamine improved liver sinusoidal perfusion, reduced leukocyte adherence
and apoptosis in both the early and late phases of IR injury. Hepatocellular injury was reduced. There was no difference in the level of tissue glutathione or tissue
and plasma F2 isoprostane levels.
This study shows that the hepato protective effect of Bucillamine in warm Liver
ischemia reperfusion injury is not by direct replenishment of Glutathione level;
however, it is through decreased neutrophil activation and recruitment. A clinical
trial could hence be undertaken in the future to study its efficacy
Light Hadron Properties From Lattice QCD
The subject of this thesis is mainly concerned with dynamics of light quarks. The question that will be attempted to answer is, What is the quark mass dependence of low lying hadrons ? In particular, this work will focus on the quark mass dependence of mesons and baryons with the tools of lattice calculations and effective field theories.
The two and three flavor effective field theories are applied to pions and kaons respectively to study the quark mass dependence of their masses and decay constants. In addition, the phenomenologically interesting Æ’ K / Æ’pi, is analysed in three flavor theory. It is found that the results of extrapolation agree with experimental results indicating that the effective field theory correctly accounts for effects of lattice calculations.
In the baryon sector, a calculation for the scalar strange content of the nucleon is performed. This quantity and the heavy quark matrix elements of the nucleon are of great phenomenological importance as they provide an estimate for the scattering cross-section of a dark matter candidate with nucleon. Within the limitation of this work, it is found the result is in agreement with the lattice average. xii
Monte-Carlo simulation of photoproduction of Omega meson
The null result of December 2004 Sub-threshold photoproduction of J/ experiment has motivated this thesis. This monte-carlo predicts the cross-section for sub-threshold photoproduction process and provides an insight on the cross-section range of these processess. The experiment was also conducted as a calibration run for Omega and Eta mesons for the verification of correctness of experimental procedure. The results from this experiment are compared with the monte-carlo simulation for the number of omega meson events. This is primarily done as the models for photoproduction of omega meson are well tested. The monte-carlo provides satisfactory results for the photoproduction models and with a crude a spectrometer model predicts the number of events which are off by a factor less than two. A refined model from Jefferson lab will eliminate this discrepancy
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Exploiting Symmetry in Dynamics for Model-Based Reinforcement Learning With Asymmetric Rewards
Recent work in reinforcement learning has leveraged symmetries in the model to improve sample efficiency in training a policy. A commonly used simplifying assumption is that the dynamics and reward both exhibit the same symmetry; however, in many real-world environments, the dynamical model exhibits symmetry independent of the reward model. In this letter, we assume only the dynamics exhibit symmetry, extending the scope of problems in reinforcement learning and learning in control theory to which symmetry techniques can be applied. We use Cartan's moving frame method to introduce a technique for learning dynamics that, by construction, exhibit specified symmetries. Numerical experiments demonstrate that the proposed method learns a more accurate dynamical model
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