Peter Kammel University of Illinois at Urbana-Champaign MuCap Collaboration V.A. Andreev, T.I. Banks, B. Besymjannykh, L. Bonnet, R.M. Carey, T.A. Case, D. Chitwood, S.M. Clayton, K.M. Crowe, P. Debevec, J. Deutsch, P.U. Dick, A. Dijksman, J. Egger, D. Fahrni, O. Fedorchenko, A.A. Fetisov, S.J. Freedman, V.A. Ganzha, T. Gorringe, J. Govaerts, F.E. Gray, F.J. Hartmann, D.W. Hertzog, M. Hildebrandt, A. Hofer, V.I. Jatsoura, P. Kammel, B. Kiburg, S. Knaak, P. Kravtsov, A.G. Krivshich, B. Lauss, M. Levchenko, E.M. Maev, O.E. Maev, R. McNabb, L. Meier, D. Michotte, F. Mulhauser, C.J.G. Onderwater, C.S. Özben, C. Petitjean, G.E. Petrov, R. Prieels, S. Sadetsky, G.N. Schapkin, R. Schmidt, G.G. Semenchuk, M. Soroka, V. Tichenko, V. Trofimov, A. Vasilyev, A.A. Vorobyov, M. Vznuzdaev, D. Webber, P. Winter, P. Zolnierzcuk Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia Paul Scherrer Institute (PSI), Villigen, Switzerland University of California, Berkeley (UCB and LBNL), USA University of Illinois at Urbana-Champaign (UIUC), USA Université Catholique de Louvain, Belgium TU München, Garching, Germany University of Kentucky, Lexington, USA Boston University, USA Contents Physics Context Muon Capture on the Proton Theory – Experiment  Cap and First Results First Physics Results from the MuCap Experiment at PSI Topics in Nuclear Physics DNP, October 28, 2006

 EW current key probe for nucleon structure  Understanding hadrons from fundamental QCD lattice QCD chiral effective field theory (ChPT)  Goldstone boson of spontaneously broken symmetry, sys. expansion in q/  model independent predictions fundamental properties and symmetry tests interesting processes (astrophysics) interface to lattice calculations … Nuclear Physics Context nucleon level quark level   (1-  5 ) u d W  W  relevant degrees of freedom ? q q charged current

Muon Capture and Axial Nucleon Structure  - + p   + n rate  S Lorentz, T invariance + second class currents suppressed by isospin symm. Vector form factors q 2 = m  2 g V = (5) g M = (25) Vector form factors q 2 = m  2 g V = (5) g M = (25) Conserved Vector Current CVC strong program JLab, Mainz,... Main motivation for  Cap studies Axial form factors q 2 = m  2 g A = 1.245(4) g P = 8.3 ± 50% Axial form factors q 2 = m  2 g A = 1.245(4) g P = 8.3 ± 50%

Axialvector Form Factor g A Exp. History Axial radius Lattice QCD  +N scattering consistent with  electroproduction (with ChPT correction) introduces 0.4% uncertainty to  S (theory) PDG 2006 Edwards et al. LHPC Coll (2006) Bernard et al. (2002)

g P determined by chiral symmetry of QCD: n  p --  g  NN FF g P = (8.74  0.23) – (0.48  0.02) = 8.26  0.23 PCAC pole term Adler, Dothan, Wolfenstein ChPT leading order one loop two-loop <1% N. Kaiser Phys. Rev. C67 (2003) Lincoln Wolfenstein, Ann. Rev. Nucl. Part. Sci … The radiative muon capture in hydrogen was carried out only recently with the result that the derived g P was almost 50% too high. If this result is correct, it would be a sign of new physics that might contribute effectively to V, A or P. Lincoln Wolfenstein, Ann. Rev. Nucl. Part. Sci … The radiative muon capture in hydrogen was carried out only recently with the result that the derived g P was almost 50% too high. If this result is correct, it would be a sign of new physics that might contribute effectively to V, A or P. g P basic and experimentally least known weak nucleon form factor solid QCD prediction via ChPT (2-3% level) basic test of QCD symmetries g P basic and experimentally least known weak nucleon form factor solid QCD prediction via ChPT (2-3% level) basic test of QCD symmetries Recent reviews: T. Gorringe, H. Fearing, Rev. Mod. Physics 76 (2004) 31 V. Bernard et al., Nucl. Part. Phys. 28 (2002), R1 Pseudoscalar Form Factor g P

 S Calculations 1%

Processes to Determine g P  - + p   + n OMC rate  S BR~ experiments, typical precision 10-15%, Saclay 4%  - + p   + n +  RMC BR~10 -8, E>60 MeV  He   + 3 H n pion electroproduction … 279±25 events BR  (k>60MeV)=(2.10±0.21)x10 -8 Wright et al. (1998) authors  stat (s -1 ) comment theory 1993Congleton & Fearing13041B theory 1996Congleton & Truhlik1502 ± 321B + 2B exp 1998Ackerbauer et al ± He TPC theory 2002Marcucci et al.1484 ± 81B+2B, T beta constraint rad. corrections?

Muon capture and muon molecular processes  T = 12 s -1 pμ ↑↓ singlet (F=0)  S = 691 s -1 n+ triplet (F=1) μ pμ ↑↑ ppμ para (J=0)ortho (J=1) λ op  ortho =506 s-1  para =200 s-1 ppμ Interpretation requires knowledge of pp  population Strong dependence on hydrogen density  pp  P pp  O pp 100% LH 2 pp pp  P pp  O 1 % LH 2 time (  s) rate proportional to H 2 density  !  λ pp 

no overlap theory & OMC & RMC large uncertainty in OP  g P  50% ? no overlap theory & OMC & RMC large uncertainty in OP  g P  50% ? Precise Theory vs. Controversial Experiments ChPT OP (ms -1 ) gPgP  - + p   + n + TRIUMF  Cap precision goal exp theory TRIUMF 2005  - + p   + Saclay

n Lifetime method  →e decays measure   to 10ppm,     S = 1/   - 1/    to 1%  n Unambiguous interpretation capture mostly from F=0  p state at 1% LH 2 density Clean  stop definition in active target (TPC) to avoid:  Z capture, 10 ppm level n Ultra-pure gas system and purity monitoring to avoid:  p + Z   Z + p, ~10 ppb impurities n Isotopically pure “protium”  to avoid:  p + d   d + p, ~1 ppm deuterium diffusion range ~cm  Cap Experimental Strategy fulfill all requirements simultaneously unique  Cap capabilities

 e  Cap Detector Design Reality 2004

3D tracking w/o material in fiducial volume Muon Stops in Active Target p -- 10 bar ultra-pure hydrogen, 1.16% LH kV/cm drift field ~5.4 kV on 3.5 mm anode half gap bakeable glass/ceramic materials Observed muon stopping distribution E e-e- Operation with pure H 2 challenging, PNPI, PSI

Time Spectra  -e impact parameter cut huge background suppression diffusion (deuterium) monitoring --  +  SR in 50G  + as reference identical detector systematics different physics blinded master clock frequency

TPC fiducial cuts Start time fit Consistency Studies Event selection cuts 6 mm Inside TPC

 Cap Unique Capabilities: Impurities Results n c N, c O < 7 ppb, c H2O ~30 ppb n correction based on observed capture yield Diagnostic in TPC rare impurity capture  Z  (Z-1)+n+  Z (C, N, O) ~ (40-100) x  S ~10 ppb purity required Hardware Circulating Hydrogen Ultrahigh Purification System Gas chromatography CRDF 2002, 2005 Imp. Capture x z t

Results Directly from data c d = 1.49 ± 0.12 ppm AMS (2006) c d = 1.44 ± 0.15 ppm On-site isotopic purifier 2006 (PNPI, CRDF)  p + d   d + p (134 eV)  large diffusion range of  d < 1 ppm isotopic purity required  Cap Unique Capabilities:  p,  d diffusion Diagnostic: vs.  -e vertex cut AMS, ETH Zurich e-e- e-e- pp p dp d or to wall  -e impact par cut World Record c d < 0.1 ppm

Muon-On-Demand concept  Cap Unique Capabilities: Muon-On-Demand Beamline Single muon requirement (to prevent systematics from pile-up) limits accepted  rate to ~ 7 kHz, while PSI beam can provide ~ 70 kHz - kV kV Kicker Plates 50 ns switching time  detector TPC Fig will be improved ~3 times higher rate dc kicked 2-Dec-2005  Lan kicker TRIUMF rf design

Corrections & preliminary results data 2004 MuCapPDG events =1/  (s -1 )  S (s -1 )1/  (s -1 ) - x   18 + x   8.3 internal correction (s -1 ) uncertainty (s -1 ) statistics 12 Z>1 impurities-146  stop definition 2  d diffusion -121  p diffusion -31  +p scatter -52 pileup11 det combination5 clock3 total systematics-339 total sys & stat-3315 external correction (s -1 ) uncertainty (s -1 ) pp  formation 194 OP transition /  in  p system 12 1/   PDG 8.3 total external369.5

 Cap and  S calculations rad. corrections Goldman (1972) Czarnecki Marciano Sirlin (2006) private comm. preliminary MuCap agrees within ~1  with  S theory Thorough theory studies needed for next MuCap 1% stage ! preliminary

within one sigma of chiral prediction, no dramatic discrepancy nearly independent of molecular physics ( OP ) has overlap with old OMC, barely with recent RMC result final result (’06 and ’07 data) will reduce error to 7% within one sigma of chiral prediction, no dramatic discrepancy nearly independent of molecular physics ( OP ) has overlap with old OMC, barely with recent RMC result final result (’06 and ’07 data) will reduce error to 7%  Cap and g P preliminary

 2006 data and 2007 plans  events  - achieved in 2006  events  + and suppl. measurements in 2007  S with 1% uncertainty   +d proposal planned for 2007 Summary and Plans  Cap theory*  S 730  g P 6.95   0.23  Preliminary results 2004 data  Ideas for ultrapure H 2 TPC welcome *including Czarnecki et al. rad. corrections preliminary