Student Abstracts: Nuclear Science at LBNL

Vertex Tracking for the Pixel Detector Group at STAR. KENNETH GARMON (University of North Carolina, Chapel Hill, NC 27514) HOWARD MATIS (Ernest Orlando Lawrence Berkley National Laboratory, Berkley, CA 94720) .
The goal of the Solenoidal Tracker at RHIC (STAR) experiment is to search for a phase transition in nuclear matter from confinement in hadronic particles to a quark gluon plasma (QGP). The STAR experiment makes use of the new Relativistic Heavy Ion Collider (RHIC) that has been built at Brookhaven National Laboratory (BNL). One important signature that a quark gluon plasma has been created is the enhanced production of D0 mesons. However, the present equipment lacks the sensitivity necessary for detecting D0 mesons. A few members of the STAR group at LBNL are now working on building a new detector component, designed specifically to detect D0 mesons. The main component of this detector will be a chip, which makes use of the new Active Pixel Sensor technology. My work in the Pixel Detector Group has mainly focused on helping to determine the best resolution for the chip. My mentor, Howard Matis, has created Monte Carlo simulations of D0 meson decays and what data will be taken as a result in the detector. My goal has been to write software (using C) that will re-create particle trajectories and find the vertex (where the D0 meson originally decayed). Once we have determined the most accurate algorithm for re-creating D0 meson decays, we can then determine the most accurate resolution for the chip. In addition, my algorithms can also be used in the final software that will be used to actually analyze data from the detector. By actually running my code using a Monte Carlo simulation, I have found that my program produces the correct answers in all except for a few cases (in which the vertex lies very close to the origin).

Gamma-ray Spectroscopy Using A Novel Sorting Routine: "Blue". SEPEHR HOJJATI (Contra Costa College, San Pablo, CA 94806) STEVE ASZTALOS (Ernest Orlando Lawrence Berkley National Laboratory, Berkley, CA 94720) .
Studying the coincident g-rays is one of the most powerful means to learn about nuclear structure. The GANDS collaboration uses GAMMASPHERE in conjunction with 252Cf (with ~3% spontaneous fission branching ratio) to study the structure of neutron-rich nuclei. For the purposes of studying the coincident relationship between g-rays, one needs to construct a database of coincident g-ray events. Blue, a computer software developed by Mario Cromaz (LBNL), provides a library of subroutines that can be utilized both to construct such a database and to access the database in the desired way by executing queries which would construct one-dimensional histograms from multi-fold database. By writing interfaces in C code, one can call the subroutines provided in Blue to produce spectra which can then be displayed using standard nuclear physics data analysis software. To date, we have read about 60 tapes into Blue and have created several multi-fold (3 through 6-fold) databases which can be used to resolve overlapping photo-peaks which are not otherwise resolvable using traditional nuclear physics databases due to the typical data compression invoked in creating such databases. Moreover, Blue reduces the size of a traditional histogram by ~1000 folds.

The Recyclotron Project. MAISHA MURRY (Tuskegee University, Tuskegee, AL 36088) MARGARET MCMAHAN (Ernest Orlando Lawrence Berkley National Laboratory, Berkley, CA 94720) .
The objectives of the Recyclotron project are to produce medium-lifetime radioactive beams, to test the limits and feasibility of working with them, and to run future reactions with these beams. To produce radioactive beams, radioactive isotopes are prepared in the 88-Inch Cyclotron. The radioactive isotopes are collected and introduced into the Advanced Electron Cyclotron Resonance source (AECR), where a charged particle beam is created and recycled back through the cyclotron to produce a beam of the radioactive isotope. However precautions must be taken to only medium-lifetime radioactive isotopes to prevent contamination of the ion source. The preliminary radioactive beam attempted was Krypton-76, which has a 14.8-hour half-life. In efforts to produce Krypton-76 there was the possibility of creating Selenium-75 with a 119.78-day half-life and Arsenic-73 with a 80.3-day half-life, which are both long-lived radioactive isotopes. It was determined during a test run on June 7, 2001 that very little of the two contaminates were produced and therefore not a problem. Future radioactive beams are anticipated such as bromine-77, -78 and Niobium-92 to study the p-process nuclei, nuclear structure and magnetic moments.

Neutral Kaon-Kaon Correlations at STAR. CHARLES STEINHARDT (Princeton University, Princeton, NJ 08544) NU XU (Ernest Orlando Lawrence Berkley National Laboratory, Berkley, CA 94720) .
Bose-Einstein statistics predict identical bosons will tend towards the same quantum state. We consider the relativistic momentum difference between a pair of kaons, and pairs of kaons from the same event, which might interact, should have a smaller difference than pairs of kaons from different events, which cannot possibly interact. Theory predicts that the ratio of the two distributions, when properly normalized, should be 1 for large values of momentum difference but should be augmented by a Gaussian of some radius and amplitude 1 for small values. The radius is the uncertainty in momentum, so the uncertainty principle lets us determine a radius of the interaction. We used data taken from Au-Au collisions at RHIC (Relativistic Heavy Ion Collider) and observed by STAR (Solenoidal Tracker at RHIC) and examined the Bose-Einstein correlation of kaons, unstable spinless bosons. The energy at RHIC is initially high enough that the kaons are in equilibrium, and we measure them after they decouple, or "freeze out". One of the reasons this is interesting is that our energies are nearly high enough to create the Quark-Gluon Plasma, a postulated state that existed just after the big bang, and a large freeze out radius would be evidence of quark deconfinement that accompanies this state. However, our preliminary results are that we do not find any correlation. This would appear to conflict with published results from other experiments and other particles, though we developed some theoretical models that remove that conflict.