1. Bo XinRare D Semileptonic Decays 14/23/2006 Studies of Rare Semileptonic D Meson Decays  Introduction  Analysis Technique  Testing the procedure  Results (  e,  ’e,  e )  Systematics  Summary Bo Xin Purdue University – CLEO collaboration APS April Meeting Apr 22-Apr 25, 2006

2. Bo XinRare D Semileptonic Decays 24/23/2006 Introduction  The results with 55.8pb-1 CLEO-c data have been published: Phys.Rev.Lett.95:181801,2005 Phys.Rev.Lett.95:181802,2005  Summing up all exclusive semileptonic branching fractions measured in this analysis we find:  These are consistent within errors but somewhat smaller than CLEO-c inclusive semileptonic branching fractions (281/pb):  There is room left for new semileptonic modes with small branching fractions, e.g. D   e,  ’e,  e

3. Bo XinRare D Semileptonic Decays 34/23/2006 The CLEO-c detector and data sample SVX CLEO III  p/p = 0.6% at 1 GeV/c  E/E = 2% at 1 GeV, 5% at 100 MeV Excellent electron and particle ID CLEO-c Pilot run starting in the fall of 2003 Note: Log Scale Beam Energy (GeV) Over 20 years of data taking at Y (4S) Beam Energy (GeV) Advantages at  (3770) –Pure, no additional particle –Low multiplicity –High tagging efficiency Data sample ~281/pb at  (3770) The generic MC sample (40X luminosity of the data).

4. Bo XinRare D Semileptonic Decays 44/23/2006 Analysis Technique  Candidate events are selected by reconstructing a D, called a tag, in several hadronic modes  Then we reconstruct the semileptonic decay in the system recoiling from the tag.  Two key variables in the reconstruction of a tag:  Define U  E miss  |P miss |  The absolute branching fraction is where  is the efficiency of finding a signal in events with reconstructed tags.

5. Bo XinRare D Semileptonic Decays 54/23/2006 Reconstruction of tags One D tag candidate per D tag flavor per mode is chosen. Examples of fits to Mbc for the following tag modes in 281 pb-1data:

6. Bo XinRare D Semileptonic Decays 64/23/2006 Test (1): D  K/  /Ks/  0 e - Generic MC & Data Same tests were made using the data, the results agree with other CLEO-c analyses very well. Test the analysis method using semileptonic modes with large yields for each tag separately and for all tags combined

7. Bo XinRare D Semileptonic Decays 74/23/2006 Test (2): D  /  ’/  e - Generic MC Procedure tested with Generic Monte Carlo Input BFs reproduced successfully

8. Bo XinRare D Semileptonic Decays 84/23/2006 Two  submodes give consistent results Results (1): D  e (DATA – 281/pb) D  e ! First observation of D  e ! Preliminary

9. Bo XinRare D Semileptonic Decays 94/23/2006 Results (2): D  ’e,  e (DATA – 281/pb) Feldman & Cousins Phys.Rev.D57:3873-3889,1998 Preliminary

10. Bo XinRare D Semileptonic Decays 104/23/2006 Systematic Uncertainties and Results OUR PRELIMINARYPDG-2004 Systematic Uncertainties

11. Bo XinRare D Semileptonic Decays 114/23/2006 Summary  Rare D semileptonic modes: D  e,  ’e,  e, have been studied using 281/pb of data at the  (3770)  D   e is observed for the first time in two  submodes:  and  +  -  0  No signal candidates are observed for D  ’e and D  e. Upper limits are set for these modes.  CLEO-c is going to collect a much larger sample at the  (3770). This sample will improve statistical precision of existing measurements and allow observations of new modes.