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Experimental Opportunities in Kaon Decays At the Proton Driver Fermilab Workshop 9 October 2004

Experimental Opportunities in Kaon Decays At the Proton Driver Fermilab Workshop 9 October 2004. Y. Wah, U of Chicago. Underlying dictum is to confront current knowledge with “precision” measurements: An obvious way:

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Experimental Opportunities in Kaon Decays At the Proton Driver Fermilab Workshop 9 October 2004

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  1. Experimental Opportunities in Kaon Decays At the Proton DriverFermilab Workshop 9 October 2004 Y. Wah, U of Chicago

  2. Underlying dictum is to confront current knowledge with “precision” measurements: An obvious way: One of the best examples is the search of edm of spin particles. Why ? Any particle with spin do not have edm unless P/T symmetries are violated. The physics is clean and clear and the effect, if observed, is an unambiguous indication beyond current knowledge. (history of neutron edm) Another obvious way: With precision measurement of paramters that can be calculated precisely. The physics is clean and clear and if observed deviated, is an unambiguous indication beyond current knowledge. (g-2 of electron, muon)

  3. Kg p n n These are special decays that belongs to the same class. B (Kgpon n) = 4.1 x 10-10A4h2 (<1% theoretical) B (K+gp+ n n) =8.9 x 10-11A4 f (r,h) (5% theoretical)

  4. Now (2004/5): E391 ~0.1 evt ~2010: JPARC ~ few tens evts KPOIO ~ few tens evts K+ ~ few tens evts O(103) events will be a reasonable goal in 2015. How to get there ? What to do on the way ?

  5. A Scenario: (Yr g data collected) 2004: Kgpon nE391:0.1 events sensitivity

  6. 2010: Kgpon n KOPIO: few tens events

  7. 2010: Kgpon n JPARC: few tens events

  8. What are the worries for Kgpon n to collect few thousand events ? • Acceptance is low : Typically only forward calorimeter as detector, all else in veto to suppress background. Typical acceptance 5%. Answer: Veto detector could be detector calorimeter also. Everybody is working on this obvious path. This also implies relatively low energy kaon beam (1 - 5 GeV) to be economical.

  9. (2) Kinematics is not favorable Neutral beam, two unmeasurable neutrinos. Answer: KOPIO: microbunching neutral beam; directions of gamma for decay vertex. This implies relatively lower kaon energy. Everybody is working on these also. This particular issue also ties with the photon veto inefficiencies, in particular, the Kg2pobackground. Veto inefficiencies improves as Egh Resolutions of g direction and vertex h as Eg i

  10. (c) Accidentals due to beam neutrons KOPIO: n/K ~ O(102) Ek~.5 GeV E391 : n/K ~ O(101-2) Ek~1.5 GeV Fermilab neutral K : n/K ~ 3 Ek~70 GeV The accidental loss and background is the limitation factor of high rate experiments. For example, a unique and key feature of CKM is to have a pure K+ beam (via rf separator) to eliminate the accidental background. The proton driver is needed to largely reduce this effect with the following scheme:

  11. A neutral kaon beam with K/n ~ O(100-1) Step1: Use proton driver to deliver max intensity proton beam to >100 GeV , hit a target to produce charged K+(and p+), focused ; then use rf separator to make a “pure” K+ beam (~ few tens GeV) very much like CKM method. (30 MHz for CKM, few GHz possible ??) Step 2: Take this strangeness enriched charged beam and hit a secondary target to produce neutral kaon beam (~few GeV). Q : what’s the resulting K rate and E spectrum ? what’s the K/n ratio ? In principle should be favorable, but ? gtest beam measurements to confirm

  12. P + P g K0 + Anything Cross section 10 mb g 1 mb g 10 GeV 100 GeV

  13. K- + P g K0 + Anything Cross section 10 mb g 10 Gev 100 GeV

  14. 2010: K+gp+ n n CERN/FNAL few tens to perheps hundred evts 2015: Assuming a “pure” K+ secondary beam is viable, tertiary Ks experiments should be done. h000= ? (should = e if QM is right [the same box diagram])Basically a 10-9 rare decay. Make me very happy to see the interference of 3p decay. Critical to have a clean beam (ie k/n>1). Similarly for h+-0. There are compelling arguments that a (e’/e)pee should be done with Ks to measure both the phase and amplitude. Proton driver will provide such oppuntunity.

  15. Conclusions: • Proton driver will be ideally suited to provide high intensity and clean kaon beams for the unique K g p n n experiments, particular the pure tertiary beams as discussed. And because of their pure short distance nature, these decays provide discovery potential on the fundemental level. • These experiments are hard, and will need step-by-step approach. We need to start and protect them nowso that by the time the proton driver arrives in 2015, we will be able to exploit fully it’s potential. There is some kind of old saying : “To do well in future, we need to do good now.”

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