Interconnections

Homer A. Neal, Jr

Paul Grannis Stony Brook University

April 12, 2014

My career has intertwined with Homer’s over several cycles

1965: Grannis PhD thesis (Berkeley, advisor Owen Chamberlain) “Measurement of the Polarization Parameter in Proton-Proton Scattering from 1.7 to 6.1 BeV “

Aside from “BeV” vs. “GeV”, both measured the same physical parameter (with different methods). Homer measured the polarization of a scattered proton when both initial protons were unpolarized. Paul used a polarized target to measure the rate difference between target polarization parallel or anti-parallel to the scattering plane normal. If the strong interaction is parity and time-reversal symmetric, both measure the same dynamical quantity.

1966: Neal PhD thesis (Michigan, advisor Mike Longo) “The Polarization Parameter in Elastic Proton-Proton Scattering from 0.75 to 2.84 GeV”

Theses

Maximum Pol vs. beam energy (HANjr thesis)

To the best of my recollection Homer and I never intersected at this stage, though Mike Longo and I were fellow students at Berkeley.

■ = Neal o = Grannis

Neal and Grannis agreed!

Our stated aim was to elucidate the strong nuclear force. The language de jour was ‘Regge poles’ and our results provided qualitative agreement. Nowadays, we formulate the strong

force by QCD, a fundamental interaction among the quark and gluon constituents of the proton. Going from the quarks to the proton is a horribly complicated process that cannot be easily calculated. Still fundamental questions remain … what carries the spin of the proton? Quarks, gluons, orbital angular momentum ... ?

Stony Brook was established 140 years after Michigan, and moved to its present site in 1962. For 10 years, mud prevailed.

1971 construction in neo-penal style architecture

(I arrived in 1966)

In 50 years (within a single generation) Stony Brook has matured into a leading research university. That growth was made possible by a series of visionary leaders and faculty.

Simons Center for Geometry and Physics

Stony Brook

Homer A. Neal, Jr – 3rd Academic Vice President and Provost 1981 – 1986

Homer arrived from Indiana where he had served as Dean for Research and Graduate Development. The President at the time was Jack Marburger, a physicist who followed an acting president (physicist Alec Pond), and a long serving president physicist (John Toll). Though we were delighted to have one of our own as Provost, we worried about an surfeit of physicists at the helm.

Stony Brook’s 9 past Provosts

By 1981, the geometric growth of Stony Brook had stopped and it was time to consolidate, burnish its reputation, and make it into a real university. Homer’s even temperament and fair-mindedness was what the institution needed at the time.

He made innovations, including: encouraged resident musical ensembles (Beaux Arts Trio) introduced campus wide e-mail (no more paper memos!) began Provostial lectures by leading worldwide figures built up the humanities, social sciences, performing arts The SBU chief development officer at the time asked Homer to prioritize gift requests drawn up by aggressive department chairs: Homer’s response typified his outlook: “How can I do that … you ask me to choose among my children!”

Homer as SBU Provost

Supporting research Starting in 1983, I was leading the DØ experiment at Fermilab. Surprisingly, there were funding shortfalls, and other projects were ahead of us in the queue. I approached the Stony Brook administration for a loan to allow us to move the construction ahead by placing large item orders in one fiscal year on the Stony Brook dime, and paying back in the next year when (presumably) DOE would deliver the next year’s funds. Overall, Stony Brook made $3.5M available (overhead free) for these forward funding purchases, and allowed us to finish construction on time for the 1992 start of operation. (And all the prefund was paid back!) I greatly appreciate the support of Homer and others in the administration who were willing bet the bank to support our research program.

Homer was unique in my experience of University Provosts and Presidents – no one I could find had anything bad to say about him! Another unique aspect was his insistence on keeping his own research program going – no mean feat for an experimental physicist whose project was in California. Homer religiously travelled to Stanford 1 week in 4 to take shifts and participate in the life of the HRS experiment. This kind of engagement of course persisted after he came back to Michigan.

This time around Homer and I were more connected, but with my commuting weekly to Fermilab and teaching while in Stony Brook, the link was not strong.

In 1986, Homer stepped down as Provost, feeling that it was time for new pursuits. He spent a year with our group in the Physics

DØ

DØ was based on high resolution, hermetic, highly segmented, unit gain, LAr calorimetry (3 cryostats to keep Ar at 80K). Small tracking volume, muons outside)

Department and became interested in the study of high energy hadron collisions with DØ at Fermilab, in which several of us were engaged. When he moved back to Michigan as chair in 1987, he brought his UM group into DØ.

The thick steel cryostat walls were a problem; at intermediate angles, particles (jets) traversing them lost energy in the ‘dead’ material

The solution: build new scintillating detectors fitting between cryostats to sample the energy flow between them and allow a correction to be made. Michigan, with Florida & Texas Arlington, designed and built these ‘Intercryostat Detectors’ (ICD).

Up to 60% energy loss in dead material

In high energy collisions, one wants to reconstruct all the created particles so as to build a complete picture of an event. Electrons, photons, muons, hadrons (jets) are all identified in the detector, but neutrinos are not. They can however be sensed by the imbalance of momentum/energy in the plane perpendicular to the incident beams. This “missing transverse energy” is

impacted most strongly by the dead material and the ICD allowed an much improved estimate. The physics program of DØ relies strongly on the ICD information as the three following examples show.

Photo of the ICD detector with the forward preshower detector (greenish) mounted in front of it.

Examples of the physics enabled by the ICD measurements

The top quark was discovered by DØ and CDF in 1995. Top quarks are produced in pairs with both decaying to a W boson and a b-quark. The b-quark creates a spray of collimated particles – a jet. In a favored mode, one W boson decays to a muon and neutrino, and the other decays to two quarks (jets). The final state is thus muon, 4 jets and missing energy from the neutrino. The ICD was crucial for sensing the neutrino in the top quark discovery. The top quark is the heaviest known elementary particle with mass of about that of a gold nucleus, and was the last confirmed constituent of matter.

Examples of the physics enabled by the ICD measurements

The W boson is responsible for weak nuclear reactions (giving the interactions that power the sun). Its mass is a critical parameter of our Standard Model. The decay W→eν gives an electron and neutrino whose transverse momenta are about half the W boson mass. Thus measuring the missing energy (from the ν) in W decays is a crucial ingredient in measuring the mass.

DØ has measured the W mass to be 80.375 ± 0.023 GeV – a precision of 0.029%

Distribution of electron transverse momentum

Distribution of neutrino transverse momentum

Examples of the physics enabled by the ICD measurements

Taken together, the top and W masses predict the Higgs boson mass. The ellipses show the precision top and W results from DØ and world combinations. The blue line shows the constraint from a Higgs mass of 125 GeV, as discovered in 2012 at the LHC.

At the Tevatron, Higgs bosons are produced in association with a W or Z boson, with Higgs decay mainly to 2 b-quark jets. DØ sought many different channels, including that in which Z→νν.

In this channel there is a huge background from QCD jet production. Accurate measurement of missing energy (purple) allows this background to be controlled.

The Tevatron found evidence for Higgs decays into its dominant mode (at 3σ)

Jet Mis-ID background

Signal (magnified)

Homer also pioneered the use of modern databases in DØ to keep track of all the calibrations and stored data.

In DØ, Homer and I collaborated closely and have published nearly 500 papers over 20 years on a broad range of subjects.

For many years, Homer has been a leader in the ATLAS experiment, while I focussed on the Tevatron, and on a possible future e+ e− collider. Recently however, I joined ATLAS and so I hope for another cycle of the helix that has wound through our careers over the past 50 years.

ATLAS ?

Thanks Homer !

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