L. Littenberg - BNL K-Rare Decays Frascati - 27 May 05 Concluding Remarks L. Littenberg - BNL K-Rare Decays Frascati - 27 May 05

Isidori Arguments

Motivation, c’d

K & MSSM

Contribution of K after LHC

E949

E787/949 Events E949 Event

Products of E787/949 SPI measurements Analysis methods

J-PARC K++ LOI Stopped K+ experiment Builds on E787/949 experience Lower energy separated beam Higher B spectrometer More compact apparatus Better resolution Finer segmentation Improved  veto (crystal barrel) Aims for 50 events Not an early experiment for J-PARC Needs beamline place on the floor $ for detector

K decay at rest Decades of experience Bckgnd <1.5 x 10-11 Almost everything well-understood Can confidently scale in most parameters Biggest questions are money and will Need appropriate beamline Need better duty cycle Need funding for detector Need collaboration Could be sure of ~50 SM events, maybe 100 if pnn2 region can be used

NA48/3

NA48/3 Ambitious in-flight attempt to get ~65 SM events with good S:B Benefits from several years of thought (CKM, etc.) Brute force approach to beam Needs some development of techniques Has reasonable toolset Equiv p* resolution 1.3 MeV/c (c.f. 2.3 for E949) Redundant background rejection methods Benefit of decay in vacuum, high energy Concerns There’s always a beam pion Unanticipated background

E391a KL0

Confronting the Enemy Run 1 expected s.e.s ~ 10-8, expected BG ~310-9 KL  gg KL  popopo KL  p+p-po KL  popo po produced at CC02 po produced at CV (?) Run 1 expected s.e.s ~ 10-8, expected BG ~310-9

Responding to experience Run I  Run 2  Run 3 Neutron background much reduced, now confronting KL decay contribution Confident they can reduce the background to < 10-9

Products of E381a Beam design & MC proofing Photonuclear SPI measurements Charged particle inefficency measurements

Deeper, more granular crystals E391a to J-PARC 50 more KL Thicker photon vetoes Deeper, more granular crystals Faster electronics Goal: 40 evts in 3 years, starting in 2009?, S:B ~ 1

J-PARC KL - Part II Evts 3 options: 180 60 290

KLOD IHEP 60 GeV proton beam - take off at 35 mr KL’s peak at ~6 GeV/c Aim to get 28 events/9 background in 3 years Could be ready to run in 2008?

KOPIO

Kinematic Separation of Signal and Backgrounds

KOPIO Products Charged particle ineff. measurements 3rd generation shashliyk Accelerator R&D Bomb detection

Future History K+ SM KL

K & Ke+e- Could enhanced endpoint of K show up in Ke+e-? With UC, predicted BR at endpoint predicted as ~10-8 That part of Ke+e- maybe 3 larger.  gives K  Ke+e- maybe 400 times smaller. In amplitude 20 times smaller Could be 10% effect in interference?