Proton Driver Meeting

12 - April - 2001
FNAL Comitium

Presentations:-

• Weiren Chou: Announcements relating to the Machine
• Y. Wah: Precision Measurement of KL -> pi0 nu nubar (KAMI)
• Ed Hartouni: Hadron-Nuclear Physics

Following transparencies from McGinnis, the main ways to increase antiprotons for Run II are:

1. increasing the yield. stack the protons. the plan is to have 5x10**12 protons per pulse. We want to increase that by about a factor of four. The antiproton source can handle this.
2. better target cooling --> liquid Li lens
3. better antiproton collection efficiency

Answers to questions asked last week.

1. Concerning the aperture in the NUMI beamline. Peter Lucas has compared 40pi and 60pi and sees that we will need to replace six dipole magnets located 300m downstream from the extraction point, at a cost of about $150k.
2. Thornton Murphy is working on the aperture question for the switchyard beamline.

Steve Holmes has asked for an investigation into the possibility of replacing the Linac with a superconducting one, which would provide a higher gradient. Holmes believes that there is a real possibility that this would be built. Weiren has found there is considerable interest around the lab. Coincidentally, Helen Edwards is holding a workshop on A0 next week, and experts from around the world will be present, providing an excellent opportunity to talk to people about this idea. One would aim for a 181m Linac with a gradient of at least 12 MV/m (current one is 6 MV/m). It would be installed during the 3-month shutdown in 2003 (intended for Si detector replacement and installation of e- cooling). One would expect a statement from the Lab before Snowmass.

Mainly this is a quick project for Run II. It is relevant to this group only as the Linac is staging for the proton driver, and so might lie partly outside the charge of this group. At the same time, it is encouraging that Management is interested in increasing the Linac energy.

A formal proposal for KAMI was submitted on 2-April-2001.

This decay mode is "golden." The CKM matrix allows the definition of six unitarity triangles. The area of each triangle is related to the `Carlsjog invariants' which relate to CP violation. One of these triangles relates to rare kaon decays. The sides are given by KL0 -> pi0 nu nubar, K+ -> pi+ nu nubar, K+ -> pi0 e+ nu. Measuring the area of this trangle accurately constitutes an important test of the SM, especially as compared to other triangles.

KAMI is a standard design detector. But it is especially hermetic. This is needed to reject multi-pi0 background. Figures of Merit:

1. KAMI would be able to do the e'/e measurement of KTeV in one day.
2. KAMI would be able to do the rare decay measurements of KTeV in three days.

In the identification of the signal, the only relevant kinematic variable is the pi0 PT (wrt the beam). KTeV has 2-3 events in the PT window, corresponding to a sensitivity in the branching ratio of about 10**07. The basic expectation for KAMI is 90 events/year.

The KTeV electromagnetic calorimeter would be reused and extended. There would be a new, high-tech photon veto mounted on the vacuum pipe. There are extensive designs, including the tricky part of pumping down the vacuum. The photon veto would based on a 90 layer Pb/scintillator sandwich. There would be a fiber tracker following the designs of D0, immersed in a magnetic field. The beam hole would contain a special crystal calorimeter to tag photons with high efficiency and distinguish them effectively from neutrons, using Cherenkov light.

A year is 2x10**7 sec. The MI would provide 7.3x10**6 pulses in a 3sec cycle with a 1sec flattop. This gives a total of 3x10**18 protons. This requires *all* of the MI, excluding even BTeV...

It would take 4-5 years to build, and would run for several years. The estimate of 90 events/year includes dead time and operational inefficiency.

It would be important to debunch the beam to reduce accidental coincidences, or at least go to 106MHz rather than 53 MHz.

If the brighter booster brings a factor of four, this means 350 ev/yr. One would have to watch out for accidentals and pileup.

This physics is complementary to B physics, which measures angles of a (different) unitarity triangle rather than the three sides, as proposed here.

There is lots of nuclear physics you can do at Fermilab uniquely. Getting more protons from an upgraded driver means that nuclear physics experiments would not compete as much for resources.

There are two interesting physics possibilities:

1. QGP quark-gluon-plasma. The phase transition appears to be subtle, which means it is important to understand the normal "hadron has" phase. This demands baseline studies.
2. Constituents inside nuclear matter at large Xbj. This is accessible through Drell-Yan production and deep inelastic lepton scattering.

Facilities to be considered: the MI at 120 GeV, and the PD at 8 GeV. In both cases, polarized beams would be particulatly interesting. This would need to be studied by the machine physicists.

QGP: strangeness production seems to be the key. CERN observes an increase in strangeness and claims this signifies a phase transition. E910 observes a natural increase in particle production. More data are needed for the process pA -> hX. Also, it would be useful to study particle production using kaon or more exotic meson beams.

Nuclear Constituents: P906 is a recent proposal to continue measurements of Drell-Yan production, similar to NuSea. This is a Fermilab niche, and the proponents are experienced. There would be an opportunity to study the interesting high Xbj > 0.2 region. Other possibilities would be to use polarized beams, or kaons at high intensity. One could also think about muon scattering at high Xbj.

For the Brighter Booster, the production of polarized proton beams for these experiments would be a real opportunity for Fermilab.