What is the Optimal Strategy for a High Statistics K + g pnn Measurement at Fermilab?

1. What is the Optimal Strategy for a High Statistics K+gpnn Measurement at Fermilab? R. Tschirhart, August 21st , 2009

2. What has been Proposed, Accepted, Un-accepted and Studied at Fermilab • Conceptual designs has been developed for a 100-event decay-in-flight charged kaon experiment driven with 120 GeV beam. Designs based on separated beams (CKM) and un-separated beams (KPlus) have been explored: http://www.fnal.gov/projects/ckm/Welcome.html These can be realized with 120 GeV stretcher operation* of the Tevatron with minimal impact on the coincident Long-Baseline Neutrino Experimental program. CERN is pursing an in-flight technique using the SPS. • Concepts have been developed for 1000-event stopped K+ and low-energy KL experiments driven by high duty factor 8 GeV proton beam. See: http://project-x-kaons.fnal.gov/ *Syphers, AD-DocDB 2222, 2849 August 21st 2009. R. Tschirhart - Fermilab

3. Summary of 8 GeV Studies: • Winter/Spring 2008: Project-X era with 200 kW of 8 GeV beam. Concepts for 1000 event K+ and KL experiments were developed based of stopping K+ techniques and a KOPIO TOF techniques with a pencil beam. • Summer 2008: Developed a concept for a 40-event/year K+ experiment driven with 30 kW of 8 GeV beam before the Project-X era using the Debuncher/Accumulator complex. Discussed with the Fermilab PAC, which encouraged consideration of experiments beyond the reach of the CERN NA62 experiment. August 21st 2009. R. Tschirhart - Fermilab

4. BNL E787/E949: Stopping K+ Experiment that established the K+->pnn decay process August 21st 2009. R. Tschirhart - Fermilab

5. CKM Detector August 21st 2009. R. Tschirhart - Fermilab

6. KPLUS Detector August 21st 2009. R. Tschirhart - Fermilab

7. The Tevatron Stretcher Concept • Can be readily realized after Run-II. • Good use of a SC machine: • 1) Match Tevatron energy to Main Injector energy. No ramping. • 2) Clean single pulse transfer from MI to the Tevatron at 120 GeV. • 3) Slow spill beam out of the Tevatron with very high duty factor. • Impact on NuMI operations is similar (~10%) to the current test-beam and E906 impact. • SEB extraction of beam is easier than at 8 GeV. Beam-charge/Beam-power is x15 better. Proposed SEB performance is comparable to 1997 TeV FT. • Keeping Tevatron “on ice” about ~$6M/year. Tevatron Stretcher power and cryo is $8M/year + staff, estimated total of about $15M/year. August 21st 2009. R. Tschirhart - Fermilab

8. How might the CKM design scale with running time, duty factor and additional acceptance? • CKM assumed 4680 hours/year of accelerator operations. • CKM assumed 5x1012 protons/3-seconds with a 33% duty factor. • CKM sensitivity based on just PNN1 acceptance. • CKM 100 event sensitivity is based on a 1x10-10 BR. CKM at the Tevatron Stretcher: 5000 hours/4680 hours = x1.1 (100x1012 protons/26-seconds)/(5x1012 protons/3-seconds)* = x2.2 (5 years of running)/(2 years of running) = x2.5 (PNN2 Acceptance = PNN1 Acceptance) = x2.0 Correction for SM Branching Ratio = x0.8 ---------- *(Instantaneous rates 80% of CKM design) x9.7 August 21st 2009. R. Tschirhart - Fermilab

9. Issues with Advancing a CKM Design • At the time of CKM’s cancellation the Total Project Cost (TPC) was estimated to be $100M in FY2001 dollars by an independent review (Temple review). This escalates to about $140M then-year (2015) dollars. • We know more now at Fermilab about the cost of SCRF and the associated infrastructure (cryo-modules, etc) The cost of the SCRF beamline was probably underestimated in 2001. • In all likelyhood the cost of CKM in then-year TPC dollars would exceed $150M. Cost drivers are: SCRF, Buildings, Instrumented long decay volume. • Fermilab is now advancing Nova ($270M TPC, 2010 construction start), and is pushing Mu2e hard ($200M TPC, 2013 construction start). • Project-X accelerator construction is being ambitiously pursued after this. • A $150M TPC project must get in line behind these planned projects. August 21st 2009. R. Tschirhart - Fermilab

10. Further Issues with Advancing Another In-flight Experiment. • The Fermilab KPlus/P940 proposal design is quite similar to the CERN NA62 design. Advancing a similar experiment does not offer much insurance to the field and arguably is not the best use of resources now that NA62 is rolling. • The CKM design arguably has greater sensitivity and better scaling performance with beam power. Nevertheless it will be hard sell to get started as a $150M TPC before the CERN NA62 experiment runs and demonstrates the viability of the in-flight technique. August 21st 2009. R. Tschirhart - Fermilab

11. 1000-event Sensitivity is not Necessarily a 3% Measurement • A 1000 event measurement requires control of systematics and backgrounds at the 1% level. Where are we at here?? • Backgrounds: e.g., What are the limits of the bifurcation technique employed by E949? • Systematics: e.g. Can acceptance and losses be understood to this level? We need to address this in any proposal that discusses a 1000-event measurement. August 21st 2009. R. Tschirhart - Fermilab

12. Tactical Advantages of Mounting a High Sensitivity Stopped Experiment at Fermilab • Technique established, sensitivity scaling is fairly robust. • Different technique than NA62. • Detector and beamline is relatively small, which means: • Existing primary beam-lines and experiment enclosures can be considered. • Existing detector solenoids (CDF/D0) can be re-purposed at relatively low cost. • Detector volume is small, which controls costs. • A then-year TPC of less than $50M is plausible, which is a conceivable schedule match to the Tevatron running as a collider through FY-2011, followed by a 1-year reconfiguration of the complex and then commissioning in 2013. August 21st 2009. R. Tschirhart - Fermilab

13. Issues • Sensitivity, Backgrounds, Systematics. • Cost, cost, cost. • Who “pays” for operation of the Tevatron? • Can a small project jump in line ahead of large projects? August 21st 2009. R. Tschirhart - Fermilab