Optimizing the green-field beta beam NuFact 08 Valencia, Spain June 30-July 5, 2008 Walter Winter Universität Würzburg

June 30, 2008NuFact 08 - Walter Winter2 Contents Introduction: Green-field scenario Introduction: Green-field scenario Beta beam for small  13 Beta beam for small  13 Beta beam for large  13 Beta beam for large  13 Summary Summary

June 30, 2008NuFact 08 - Walter Winter3 Green-field scenario No specific accelerator, L,  No specific accelerator, L,  Two possible isotope pairs Two possible isotope pairs Different luminosities: Typically Different luminosities: Typically – useful ion decays/year for neutrinos useful ion decays/year for antineutrinos –5 years nu + 5 years antinu running  Corresponds to Luminosity scaling factor (LSF) = 1 LSF scales useful ion decays (integrated over t) x detector mass x efficiency –Specific detector technology: WC, TASD, MID, etc. Detector mass will be given separately (fct. of technology)!  Optimize the parameters (isotope pair, LSF, detector technology, L,  ) for the best physics output ( )

June 30, 2008NuFact 08 - Walter Winter4 Isotopes compared: Spectrum Example: Unoscillated spectrum for CERN-INO Example: Unoscillated spectrum for CERN-INO Total flux ~ N   2 (forward boost!) (N  : useful ion decays) Total flux ~ N   2 (forward boost!) (N  : useful ion decays) (from Agarwalla, Choubey, Raychaudhuri, 2006)  Peak E ~  E 0 Max. E ~ 2  E 0 (E 0 >> m e assumed; E 0 : endpoint energy) (E 0 ~ 14 MeV)(E 0 ~ 4 MeV)

June 30, 2008NuFact 08 - Walter Winter5 Want same neutrino energies (=same X-sections, L, physics=MSW, …): Peak energy ~  E 0, flux ~ N   2  Use high  and isotopes with small E 0 or low  and isotopes with large E 0 for same total flux Example: N  (B,Li) ~ 12 N  (He,Ne),  (He,Ne) ~ 3.5  (B,Li) Want same neutrino energies (=same X-sections, L, physics=MSW, …): Peak energy ~  E 0, flux ~ N   2  Use high  and isotopes with small E 0 or low  and isotopes with large E 0 for same total flux Example: N  (B,Li) ~ 12 N  (He,Ne),  (He,Ne) ~ 3.5  (B,Li) NB:  : Accelerator dof versus N  : ion source dof Where is the cost/feasibility break-even point? NB:  : Accelerator dof versus N  : ion source dof Where is the cost/feasibility break-even point? NB: Peak energy determines suitable detector technology! NB: Peak energy determines suitable detector technology! Different isotopes: Some thoughts

June 30, 2008NuFact 08 - Walter Winter6 Small  13 : Optimize  13, MH, and CPV discovery reaches in  13 direction Small  13 : Optimize  13, MH, and CPV discovery reaches in  13 direction Large  13 : Optimize  13, MH, and CPV discovery reaches in (true)  CP direction Large  13 : Optimize  13, MH, and CPV discovery reaches in (true)  CP direction What defines “large  13 ”? A Double Chooz, Day Bay, T2K, … discovery? What defines “large  13 ”? A Double Chooz, Day Bay, T2K, … discovery? Beta beams for small versus large  13 (3  m 31 2 = eV 2  Optimization for small  13 Optimization for large  13 T2KK Beta beam NuFact

Beta beams with excellent  13 reach

June 30, 2008NuFact 08 - Walter Winter8 Minimum wish list Assume that Double Chooz … do not find  13 Assume that Double Chooz … do not find  13 Minimum wish list: Minimum wish list:  confirmation of  13 > 0 –3  mass hierarchy determination –3  CP violation determination For as small as possible (true)  13 Two unknowns here: Two unknowns here: –For what fraction of (true)  CP ? One has to make a choice (e.g. max. CP violation, for all  CP, for a CP fraction 50%, …) –How small  13 is actually good enough?  Minimal effort is a matter of cost!  Minimal effort is a matter of cost!

June 30, 2008NuFact 08 - Walter Winter9 Optimal  A matter of cost! Fix L/  =1.3, LSF = 1.6 Fix L/  =1.3, LSF = 1.6 The higher , the better (modulo detector!) The higher , the better (modulo detector!) (Huber, Lindner, Rolinec, Winter, 2005) 500 kt50 kt

June 30, 2008NuFact 08 - Walter Winter10 Optimal baseline? A matter of the performance indicator, detector, , … (Huber, Lindner, Rolinec, Winter, 2005) L/  =2.6 L/  =0.8 L/  =1.3L/  =2.1 Points towards two baselines!  CP = 0  CP =  /2

June 30, 2008NuFact 08 - Walter Winter11 Isotope pair comparison:  13 sensitivity MID (50kt), LSF=1 MID (50kt), LSF=1 Two set of baselines can be identified: Two set of baselines can be identified: –Short (L/  =0.8 or 2.6) –Long (magic) Long baseline better for B/Li if  > 350 Long baseline better for B/Li if  > 350 (Agarwalla, Choubey, Raychaudhuri, Winter, 2008) Magic baseline

June 30, 2008NuFact 08 - Walter Winter12 A matter of luminosity? Isotope pairs compared: Short vs. long baseline Gamma increase: ~ 3.5 Same physics for ~ 10 x luminosity (Agarwalla, Choubey, Raydchaudhuri, Winter, 2008) MID, 50kt

June 30, 2008NuFact 08 - Walter Winter13 MH and CPV for  ~ 500 MH: Use (B,Li) at magic baseline; energy! MH: Use (B,Li) at magic baseline; energy! CPV: Use (Ne,He) at short baseline (different detector?) CPV: Use (Ne,He) at short baseline (different detector?) MID, 50kt (Agarwalla, Choubey, Raydchaudhuri, Winter, 2008)  CP dependence

June 30, 2008NuFact 08 - Walter Winter14 Optimal green-field scenario for small  13 Use two baselines, two isotope pairs: Use two baselines, two isotope pairs: –(B,Li) at magic baseline for MH sensitivity Detector: MID, TASD, … –(Ne,He) at short baseline for CPV sensitivity Detector: TASD, WC, MID?, … Either one for  13 sensitivity Either one for  13 sensitivity (For two-baseline implementations, see: Coloma, Donini, Fernandez-Martinez, Lopez-Pavon, 2007; Agarwalla, Choubey, Raydchaudhuri, 2008)

Beta beams for large  13

June 30, 2008NuFact 08 - Walter Winter16 Minimum wish list Assume that Double Chooz finds  13 Assume that Double Chooz finds  13 Minimum wish list easy to define: Minimum wish list easy to define: –5  independent confirmation of  13 > 0 –3  mass hierarchy determination for any (true)  CP –3  CP violation determination for 80% (true)  CP For any (true)  13 in 90% CL D-Chooz allowed range!  What is the minimal (effort) beta beam for that?  What is the minimal (effort) beta beam for that? NB: Such a minimum wish list is non-trivial for small  13 NB: Such a minimum wish list is non-trivial for small  13 NB: CP fraction 80% comes from comparison with IDS-NF baseline etc. NB: CP fraction 80% comes from comparison with IDS-NF baseline etc. (Sim. from hep-ph/ ; 1.5 yr far det yr both det.)

June 30, 2008NuFact 08 - Walter Winter17 Minimal effort beta beam Minimal effort = Minimal effort = –One baseline only –Minimal  –Minimal LSF –Any L (green-field!) Example: Fix LSF and optimize L-  Example: Fix LSF and optimize L-   Sharp cutoff by MH from left, from CPV from bottom  Use fixed L >= 730 km to avoid fine-tuning (Winter, arXiv: ) Sensitivity for entire Double Chooz allowed range! LSF=1

June 30, 2008NuFact 08 - Walter Winter18 Luminosity scaling for fixed L What is the minimal LSF x  ? What is the minimal LSF x  ? (Ne,He): LSF = 1 possible (B,Li): LSF = 1 not sufficient (Ne,He): LSF = 1 possible (B,Li): LSF = 1 not sufficient But: If LSF >= 5:  can be lower for (B,Li) than for (Ne,He), because MH measurement dominates there (requires energy!) But: If LSF >= 5:  can be lower for (B,Li) than for (Ne,He), because MH measurement dominates there (requires energy!) (Winter, arXiv: ) (100kt) (500kt) only  < 150!

June 30, 2008NuFact 08 - Walter Winter19 Minimal  beta beam (Winter, arXiv: )

June 30, 2008NuFact 08 - Walter Winter20 Minimal beta beam at the CERN-SPS? (  fixed to maximum at SPS)

June 30, 2008NuFact 08 - Walter Winter21 Summary Optimal beta beam for small  13 : Uses two baselines, two isotope pairs: Optimal beta beam for small  13 : Uses two baselines, two isotope pairs: –(B,Li) at magic baseline for MH sensitivity Detector: MID, TASD, … –(Ne,He) at shorter (L/  ~ 1) baseline for CPV sensitivity Detector: TASD, WC, MID?, … Minimal beta beam for large  13 : One baseline only: L >> 500 km Minimal beta beam for large  13 : One baseline only: L >> 500 km –Use (B,Li) if high enough useful ion decays LSF ~ 5:  > 80 –Use (Ne,He) if LSF ~ 1:  > 190  Minimal  will be determined by baseline and Double Chooz result

Backup

June 30, 2008NuFact 08 - Walter Winter23 Comparison of setups (Huber, Lindner, Rolinec, Winter, 2005) 3 

June 30, 2008NuFact 08 - Walter Winter24 Mass hierarchy determination (Agarwalla, Choubey, Raychaudhuri, Winter, 2008)

June 30, 2008NuFact 08 - Walter Winter25 CP violation determination (Agarwalla, Choubey, Raychaudhuri, Winter, 2008)