Brief Background on Terms and Equipment Used for Electroproduction of Lambda (1520) Particles




This page contains a very cursory overview of the equipment and some general information about the physics behind the analysis of lambdas, specifically, and analysis of events in general. This page will also primarily involve a bunch of links to outside information, where more specific details can be obtained.

The equipment involved in the physics (actual event generation, not simulation) is the Thomas Jefferson National Accelerator Facility. Here is where the actual experiments take place. In the case of my research this summer, the Lab's Hall B is where the CLAS (CEBAF Large Acceptance Spectrometer) is located. This is the equipment that is being simulated by the software I have been working with this summer. In the previous section, on the software aspects of my work, are some images of events in a representation of the CLAS.

The CLAS essentially works by taking a stream of electrons (in this case) and directing them into a proton target (in this case) and analyzing the results using various detection systems and electronics. The CLAS drift chambers (internal parts of the CLAS) can be seen also in the Hall B page at this site. There are three drift chamber regions, as can be seen at the previous link, which are essentially designed for detection of charged particles.

The second layer of detection involves the Cerenkov counters, which are particularly useful for detection of electrons in the CLAS. More information on the Cerenkov counters can be found here. Following the Cerenkov counters are the time-of-flight scintilators, which are used to more precisely locate the tracks in a particular event. This layer of detection, therefore, is particularly important and can be more fully understood by studying this link.

Finally are the electromagnetic calorimeters, which "slow down" the particles after they've passed through the inner components of the CLAS. They also relay information on the energies of the particles as they pass through the calorimeters. There are several sections on the electromagnetic calorimeters on the Hall B website, as well as the previously linked information on the other components of the CLAS.

In terms of the physics aspects of my research, the reaction being studied (or to be studied once the software is 100% running) is the following:

ep -> e'Lambda(1520)Kaon


Some of the important values that were dealt with during my research were Q^2 and W. Q^2 and W are calculated below; this was also part of the code used in the trkmon histograms, three of which were displayed in the previous research section.


Efinal = sqrt(pmom**2 + mass**2)
theta = acos(Cz)
Q2 = -4*Ebeam*Efinal*( sin(theta/2)**2 )
nu = Ebeam - Efinal
W2 = Q2 + Mp**2 + 2*Mp*nu

W = sqrt(W2)

From the above, 'pmom' is the momentum of the particle being detected, 'mass' is the mass of that particle, 'Ebeam' is the energy of the accelerated beam of electrons (in this case), 'Mp' is the proton mass and 'Cz' is the directional cosine of the particle's track. This information, although I haven't had the opportunity to study it in depth, can be somewhat useful in understanding the physics-oriented goals of my research. However, if you are more interested in what I actually did work on in depth, the previous page has more relevant information.


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