Timothy J. Hallman

This is the first in a series of interviews of Collaborators that will be published in the STAR Newsletter. To kick things off, I've asked Tim to be the first person to be interviewed.

Tim is originally from Milford, Connecticut. After graduating from Muhlenberg College in Allentown, PA in 1974, Tim took a year off before beginning his graduate studies at Johns Hopkins University. In 1982 Tim received his Ph.D. and began a post-doc at Johns Hopkins. Tim was briefly a staff member at LBNL (1991) before becoming a research faculty member at UCLA. Tim moved to his current position at BNL in 1996.

Tim has a few recommended eateries on Long Island. One is the Sea Basin in Rocky Point. Tim also recommends the Chinese/Japanese restaurants as well, Kirin and Benten just to name two.

Tim became Spokesperson last year after an exciting election. Tim shares his thoughts on the elections, run plan, and life experiences below.

SNL: Who/what was the driving force that got you interested in heavy ion physics?

TJH: My thesis advisor, Leon Madansky, was the person most directly responsible. He became intrigued by this field due to theoretical predictions about Lee-Wick matter, and because of the (then) exciting apparent observation of coherent pion production in proton induced interactions in emulsion at the Princeton Particle Accelerator. This turned out later to be a difficulty with properly determining the grain density for beam protons in emulsion, but by then JHU was already staging an inclusive pi zero measurement at the Bevalac at LBNL. I had worked for Madansky as a teaching assistant, and he decided to try me out as a research assistant.

SNL: Which experiments have you worked on?

TJH: I can not remember all the numbers precisely; when I was a postdoc at Johns Hopkins, I was involved in two experiments at TRIUMF (pi and mu capture), a number of experiments at the Bevalac (subthreshold pi,k,pbar searches, single lepton experiment, the Di-Lepton Spectrometer), and a number of experiments at the AGS (lambda polarization/particle & strangeness production in heavy ion collisions (810), lambda & sigma polarization in pp collisions (813, 817), pbar-nucleus interactions (cold QGP) , and search for dbars/strangelets (858) and Hzero Di-baryons (896).

SNL: You've been with STAR from the beginning. Is the STAR of today what you had envisioned back then?

TJH: I think so; I always felt this was a very important project for nuclear science, and that it would do well because of one reason; a lot of talented, dedicated people.

It was also important that the construction project got its first inertia at LBNL where there was a very talented staff used to building large detectors. We are still completing/chasing some of the detector capability envisioned in the original scope (EMC, TOF) because of funding constraints, but the STAR of today has already fulfilled much of the promise of what was said in the CDR, and the future looks really exciting both near and far term. I have to emphasize again it is really the people of STAR who make this work. I am always reminded of something that was said at the March 1993 review at LBNL when STAR was finally approved for construction. Someone on the panel (perhaps the Chair) said, "well, the design looks about right, and the cost seems about right, but we really can't tell you if this will be a success; that will depend on whether or not you have the right people." I think the history both of the construction project and the first analysis shows we indeed have the right people. We have a great team in STAR, and I really enjoy working with everyone on it.

SNL: I imagine that there were many iterations to the initial STAR detector design. Is there anything that was iterated out that you would like to have seen implemented?

TJH: With respect to the initial design, the thing I think is still very important to

pursue is the barrel TOF. There is a very good, viable, inexpensive technical solution for this detector now, and it will extend STAR's physics reach significantly, more than we probably can even determine at the moment, since important "features" of the final state that require PID at intermediate pt are still being "discovered". Of course some very important additions that were not in the original scope have also been added; the EEMC which will make the STAR spin program world class, the SSD, PMD, FTPC's-all are capable of enriching the STAR science program significantly. One of our near term challenges is to bring these detectors in addition to the BEMC and SVT into efficient operation along with the baseline detectors and integrate the information from all of them to get as complete a picture as possible of the conditions produced in ion-ion collisions at RHIC.

And no-I didn't forget the FPD. It has already created a lot of renewed interest in transverse spin asymmetries, and their possible interpretation in terms of transversity and/or parton orbital motion. The richness of the spin program we intend is fantastic. We shouldn't forget either that the FPD may give us the first direct measurement at RHIC of the gluon distribution in the Au nucleus from the d+Au run. That would be very exciting.

Of course now we are embarking on a future program; there are new horizons before STAR, new exciting physics challenges, and we need to form a new strong team of young folks who would like to take STAR the next step. That is something we will be talking more about in the coming months.

SNL: Your long-standing commitment to STAR eventually led you to become Spokesperson in 2002. Could you briefly describe how you became the Spokesperson? What was the journey like?

TJH: I would like to think that the opportunity was a possibility for me because of my service and work for the Collaboration over the years. I can say without hesitation STAR has been the priority for my professional career since joining in 1991. Over such a long period, people have a chance to work with you and judge your abilities. I think this was a factor in their assessing whether I could do the job. I owe a great deal in that respect to John Harris and Jay Marx. For most of that period I was assisting as Deputy Spokesperson. Working with John and Jay provided invaluable knowledge and experience without which I would surely not be prepared for this responsibility. When I started I was enthusiastic and willing to work hard, but pretty green on anything the size of STAR.

SNL: The election for Spokesperson was very contentious. Do you think the elections damaged the collegiality of the collaboration? If so, has STAR recovered?

TJH: I hope we have recovered. I have worked as hard as I can to be "everyone's Spokesperson". That doesn't mean I agree with everyone; sometimes hard choices need to be made and not everyone is going to agree. But I try to be fair and open with everyone, and to work as hard as I can to make STAR work for the people who work for STAR. I think that is (has been) perhaps a key to our moving forward. The point is that there is so much great science in our hands, that's where our energies need to go. I think most people feel this, and that has been an important factor in our moving forward. This is the kind of exciting time that may happen once in a career.

SNL: What has surprised you the most since you became Spokesperson?

TJH: I had a lot of experience helping as Deputy Spokesperson, so not too much has surprised me on the everyday front. Like everyone else, I find the high pt results from the last runs very intriguing and look forward to the insight d+Au will provide. I would like to imagine as a Collaboration we will take some time in the near future to assess all the interesting results we have from the first runs (HBT, v2, strangeness, spectra, event-by-event observables, etc...) and have a probing scientific discussion about what these things are telling us-and what they are not.

I also find the large analyzing power of the inclusively produced forward pi zeros very exciting.

SNL: Are you happy with the progress of the collaboration?

TJH: You know, so many people are doing such an outstanding job, this is almost a funny question to answer. I think we're doing great, and it's because we have a great team. The challenge I foresee is really coming up to speed fully on detailed planning (physics and detector) and R&D for the future, while we keep up this great productivity on our science program. It is going to be a real challenge, but we've met those kinds of challenges before, and I am confident we can do it again.

SNL: STAR has produced a lot of physics from the first two runs. We're in a great position for this upcoming d+Au run. How do we keep the ball rolling? What is your view of the run plan for year four and beyond?

TJH: It is reasonably clear to me personally, that the main focus of run 4 will be a long AuAu run. Top priorities will be open charm, v2 of multiply strange baryons, and J/Psi-- as well as extending the reach of our present pt measurements in AuAu. Among our other challenges, there are important things (like ITTF (STI), DAQ100, etc) that have to be implemented and working well if we are going to make full use of this beam, and stay fully competitive. So, next summer there will be lots to do. It is also very important e.g. that we try to get a significant J/Psi sample from this d+Au run to have a reasonable reference, since another p(d)+Au run might not come for several years.

The run configuration the following year will be a discussion in STAR and may also be controversial between STAR and PHENIX. Run V will be the first run where all the essentials (strong snake, BEMC, EEMC, gas-jet polarimeter) will be in place to make a truly robust measurement of delta G. I suspect that may be a STAR priority. It is possible (I don't think anyone knows right now) that ion collisions with lighter species may be a PHENIX priority to further map out the J/Psi suppression story. If other ion species are not done during run V it makes it all the more crucial that we get a sample of J/Psi from the present d+Au run. Otherwise, it is possible we would not be as competitive in the charmonium game as we would like, having a AuAu measurement, but not a reference spectrum, which is essential.

SNL: There is a lot of exciting R&D being done for the future STAR detector. The focus, however, seems to be on the distant future where there will be a completely reformed STAR. How do you envision the transition period from our current technology to the next generation STAR detector RHIC II?

TJH: Based on what the upgrades steering committee has done so far and the outcome of the Bar Harbor meeting, I would say the future is now. There are a number of important upgrades we need already in 2006-2007 to attack various physics signals we know will be key: charm thermalization, v2 of multiply strange baryons and D's, event structure characteristics. These are going to be essential to confirm we are producing an equilibrated partonic system and to measure its properties. These mid-term upgrades (including DAQ, FEE, TOF, muvtx, LIII) will serve STAR well into the next decade; the main additional thing that will be needed is a new TPC. The development of a GEM readout for that device will be getting into high gear this year. We would probably begin constructing a new TPC in 2008 although the timing for that needs to be studied further.

Another item we haven't focused strongly on yet, but which I think is probably going to be essential is a layer of some kind of tracking (silicon, GEM) in front of the EEMC. That is because we need enough resolution on charge sign to distinguish W+ and W- for the spin program. That may be difficult with the present tracking by itself. Other detector components like roman pots may be in STAR's future as well. We have some near term homework from Tom Kirk to prepare a detailed statement of our plans for the BNL Program Advisory Committee by June. I am confident we will have that ready.

SNL: What do you consider the most urgent task right now for you as Spokesperson?

TJH: I see a couple of high priority things that I need to work on in the near term.

The first is focusing the collaboration on a thoughtful discussion of what we have learned in the heavy ion program so far, and what key things have priority to be measured. This needs to be more than a casual discussion; we need to really take a careful look and wrestle with ourselves, to the extent the data and available models will support, to examine what we think we have learned.

Equally important is getting the effort on STAR's near and long term detector upgrades into full swing. This is the moment that need's to happen, and finding the necessary manpower is going to be a challenge.

I have some other goals as well which are very important for me; one is strengthening some of the things we do to manage the collaboration, improving our web site, documenting things better, etc. Also I want to continue to work hard to restore collegiality and mutual respect in some sectors of the Collaboration where there have been problems in the past.

SNL: What do you hope to be doing 10 years from now?

TJH: Looking at how fast things have developed in the last 10 years, it is pretty hard to judge the next ten. I would be happy if I were helping some young people pursue their science on STAR/RHIC.

SNL: Any advice for the junior STAR members?

TJH: I would say they should have fun. That may sound funny since they "carry the

ball" on so much in STAR, and are so busy; but if its possible to take a step back, I hope they can appreciate the moment; it is a really unique time in terms of new science being (maybe) just around the corner. Many people don't ever experience that even though they may have very distinguished careers. Promoting young people and providing them with good opportunities for their career has always been a priority for STAR, and it will continue to be so. So, I would say they should have some fun, (work hard); we will work hard to make sure that STAR is a great platform for them to further their career.

SNL: Thank you for your time Tim!

TJH: My pleasure.

If you would like to see someone interviewed, or would like to contribute an interview, please e-mail me at ETYamamoto@lbl.gov.