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Vaandering, Eric Wayne (Ph.D., Physics)

Mass and Width Measurements of Baryons

Thesis directed by Professor John P. Cumalat

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Analyses of several charmed baryons decaying to are presented. The data for these analyses were collected by FOCUS, Fermilab Experiment E831. FOCUS is a high statistics charm photoproduction experiment and accumulated data during the 1996-1997 Fermilab Fixed Target run.

In an analysis of the decays $\sigc \to \lc \pion^{\pm}$ we measure the $\sigc-\lc$, $\scd-\scz$, and $\scp-\scz$ mass differences. We find $\mdsczlc = \ensuremath{167.54}\xspace\pm \ensuremath{0.19}\xspace\pm \ensuremath{0.34}\xspace~\mevcc$, $\mdscdlc = \ensuremath{167.59}\xspace\pm \ensuremath{0.20}\xspace\pm \ensuremath{0.27}\xspace~\mevcc$, and $\mdscdscz = \ensuremath{0.05}\xspace\pm \ensuremath{0.28}\xspace\pm \ensuremath{0.09}\xspace~\mevcc$. In an analysis of the decay $\lcpiz$ we find $\mdscplc = \ensuremath{168.03}\xspace\pm \ensuremath{1.01}\xspace\pm \ensuremath{0.30}\xspace~\mevcc$ and $\mdscpscz = \ensuremath{0.49}\xspace\pm \ensuremath{1.03}\xspace\pm \ensuremath{0.45}\xspace~\mevcc$. These results are obtained with a sample of $362\pm36$ decays, $118\pm40$ decays, and $487\pm41$ decays. The results with charged pions are improvements on the best available measurements

Using a cleaner analysis of $\sigc \to \lc \pion^{\pm}$ decays, we measure the widths of and . We find $\Gamma(\scz) = 2.58\xspace\pm 0.79\xspace \asserror{0.51}{0.55}$ and $\Gamma(\scd) = 2.53\xspace\pm 0.77\xspace\asserror{0.51}{0.56}$ . These results are obtained with a sample of $425\pm55$ decays and $540\pm59$ decays. There are no published measurements of the widths.

We also report on the observation of two excited charm baryon resonances decaying to $\lc \pi^\pm$. These states are interpreted as the and with $I(J^P) = 1(\frac{3}{2}^+)$. We obtain preliminary measurements of the properties of these states of $m_{\sczs} - m_{\lc} = 232.7 \pm 1.2~\mevcc$, $\Gamma(\sczs) = 9.4\pm3.7~\mevcc$, $m_{\scds}- m_{\lc} = 234.2 \pm 1.5~\mevcc$, and $\Gamma(\sczs) = 23.6\pm4.5~\mevcc$. These measurements are compatible with the only previous observation, but no attempt is made to optimize statistical errors or determine systematic errors.

Finally, we report on a search for the doubly charmed baryons and in the decay modes $\xicc \to \lc \kaon^- n \pion$. No compelling evidence for the existence of doubly charmed baryon states is observed.

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For Mom and Dad

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Acknowledgments

A high energy physics experiment of the magnitude of FOCUS is an accomplishment which is shared by many, many people. For this reason, any acknowledgments section would be remiss in not first thanking each and every member of the FOCUS collaboration as well as the many engineers, technicians, and students who have worked on the experiment. The FOCUS collaboration is truly a unique group of people: hard working, intelligent, personable, and fun loving.

Within this collaboration, numerous people must be singled out for their particular accomplishments, without which FOCUS may well have failed.

First, thank you to everyone who built detectors. Special thanks to those who built the IE. Eric Erdos, John "the sander man" Cumalat, Luca Cinquini, and Brian O'Reilly. Thanks also to everyone who helped us pull the RG-8 cables: Iuri Pepe, Luis Méndez, Hasaan Mourad, Carlos Rivera, Enrique Montiel, David Olaya, and the many others whom I've forgotten. Whose great idea was that, anyway? Finally, thanks to Roy Justice who was always willing to help anyone (and to tell jokes that would make the Venus de Milo blush).

Thanks to Francesco Prelz who tirelessly kept the DAQ running like a champ.

Thanks to Joel Butler for writing and developing the Pass1 software. Thanks also to Irwin Gaines, Alberto Sanchez, and especially Jon ``Bad Cop'' Link for being ``Pass1 Czars'' along with me. It was too big of a job for Jon and me; you saved our sanity. Thanks, too, to the collaborators who ran Pass1 shifts, especially those who didn't page me at 6:00 am.

Thanks to Matt Nehring and Luca Cinquini for spear-heading the Skim1 project. These guys stepped into a project no one was even thinking about and made it a reality. Thanks also to John Cumalat, Brian O'Reilly, Eduardo Ramírez, David Olaya, and all the Vandy guys for running Skim1 shifts.

Thanks to everyone who developed and ran Skim2 and copied tapes, but special thanks to Harry Cheung. He coordinated, started first, finished first, and he processed my data.

Thanks also to those who have helped me along this final path of analysis with suggestions, encouragement, and enlightening discussions. Jim Wiss, Paul Sheldon, Phil ``The Million Mile Man'' Yager, Harry Cheung, Will Johns, and Kevin Stenson.

Special thanks to the two people who (in addition to John) have written letters of recommendation: Joel Butler and Jim Wiss.

Working with such a great group of people, it's impossible not to form meaningful and (I hope) long lasting friendships.

• Jon Link, for being willing to conspire with me on just about anything and for being an good person to bounce ideas off of.

• Brian O'Reilly, for among other things, taking care of me the famous Messrs. V, W, X, Y, and Z night. (I won't mention that is was partly his fault that I was in that condition to begin with.)

• Will Johns, for being a great and thoughtful housemate and for giving all of us an ideal to look to.

• Harry Cheung, who is always willing to include the new arrivals in social activities.

• Kevin ``I don't even know 'er'' Stenson, for being an all around great friend and an excellent travel agent/partner.

Outside of our collaboration, there are many people at Fermilab who deserve a recognition too. Thank you to the Farms group of the Computing Division, especially Tanya Levshina, Marilyn Schweitzer, and Mike Wolbers for helping us through the process and always being willing to throw a couple thousand more MIPS our way. Thanks also to the engineering staff for designing detector supports that could hold an elephant.

Being uprooted from ``home'' and sent off to the far off land of the Fermilab village can be a traumatic experience. Fortunately there were plenty of people who befriended me and made the process easier. The Users Center gang was crucial to my survival those two years on the prairie. Forest, Renee, Rich, and Chuck (or Chuck and Rich) thank you. And special thanks to Nancy Joyce for being a barkeep who was equally willing to talk as to listen, for always being willing to give a poor grad student a break, and for showing up bearing gifts whenever a party was running low on beer in the wee hours of the morning.

Of course, I had many friends during my two stints in Boulder too.

First, I want to thank both sets of housemates I've had. Kim King, Heather Robinson, and Sarah Simpson-Parks saw me through my difficult second year of grad school and understood (or at least pretended to) when I came home from taking comps and just wanted to ``sit.'' Thanks also to my current housemates, Greg Rakness (who's spent just as many days on ``the frontier of knowledge'' as I have), Orion Poplawski, and Marc Welliver. They have been quite understanding this last year.

Thanks also to all my fellow classmates, my support network during the first year or two of graduate school, especially Keith, Jim, Darren, Kristan, and Sarah. We suffered together and we made it, each in our own way.

Thanks to Kerstin Kirschenbaum for sharing with me the love of the solitude of the wilderness and for being a wonderful backpacking partner.

Thanks to my friend Brian King for making me realize, in an indirect sort of way, that life ain't so bad.

Away from Boulder, special thanks go to Jennifer Johnson. First for being a constant and special friend. Second, for helping me to not take myself too seriously. And finally, for providing a welcome and important diversion right at the end of my writing.

Of course, the list of people who have helped me and guided along my educational and personal path didn't begin with my graduate school experiences.

While my earliest memories are somewhat hazy, I do remember that my 2nd grade teacher, Jean Portenga was one of the first to encourage my scientific predispositions, giving her own time to challenge a young mind.

While I had many excellent teachers in high school, two stand out above the crowd. Arley Bouwma, for impressing on me that science isn't just important, it can also be fun. And Dave VerMerris for being so many things: a marvelous teacher, a cheerful man who always had a smile on his face, a motivator, and above all a role model.

My college experiences at Valparaiso University were no different. I was again guided by many wonderful professors who must be thanked. Malcolm Reynolds for his methodical and thorough (read ``lots of homework'') way of giving me a foundation in calculus and differential equations. Stan Zygmunt, for his clarity and energy. Donald Koetke for his excellent teaching and for encouraging my interest in research. Robert Manweiler for taking me under his wing and for being a confidant and mentor. And both Bob and Bruce Hrivnak for adopting me into their families, so to speak. Thank you, all of you.

Also during my undergraduate years, I spent three summers and two semesters working with people at Argonne National Laboratory. While everyone I met there was wonderful, two people deserve special recognition. Thanks to Hal Spinka for advising me and teaching me to believe in myself. And thanks to David Grosnick for doing the same and being another of my mentors and an all around great guy. My experiences at Argonne, more than anything else, helped me realize that I wanted to be a research physicist.

Of course, formal education is just one set of influences. Many other people have made substantial contributions to get me to this point.

First, my childhood neighbor, Percy Dowell, comes to mind. He was an uneducated man, who always told me ``You just keep going to school. Once you learn something, no one can take that away from you.'' Of course, I may have followed his advice to the extreme.

Second, my grandmother, Liz Huizenga, has had an enormous influence, not only on me but on our entire family. Because she was needed on the family farm, my grandmother never attended school past the eighth grade. That didn't stop her from continuing to learn new things all through her long life, and becoming, in a way, one of the most educated people I've ever known. It also didn't stop her from passing on to her children and grandchildren a love of learning unparalleled in my experience. My deepest regret is that she is not alive to see the first of her descendants receive a Ph.D.

To my parents, I owe everything. Throughout my life, they have encouraged me in everything I ever wanted to do. At great hardship to themselves, they made sure I had every opportunity they could possibly give me. They have made sacrifices that I can never fully understand or appreciate. And they never questioned my choices. Who I am is a direct result of who they are, what they have done, and what they believe in. Thank you.

Finally, to my advisor John Cumalat, I owe my deepest appreciation and admiration. John has always been a fount of ideas: many of them good, all of them interesting. He has also trusted my instincts and tried to guide rather than direct me. And he's done all this with an energy I can scarcely imagine. I couldn't imagine a better advisor. I feel very fortunate to count him, not only among my collaborators, but among my friends.

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