FIRST RESULTS from the CLEO-c DETECTOR The CLEO-c Physics Program The CLEO-c Detector The CLEO-c Run Plan Preliminary Results on the  (3770) Preliminary Results on D decays at threshold Conclusions John Yelton University of Florida Gainesville, FL

The CLEO-c Physics Program The CLEO collaboration: Carleton, Carnegie Mellon, Cornell, Florida, George Mason, Illinois, Kansas, Northwestern, Minnesota, Pittsburgh, Puerto Rico, Purdue, Rochester, RPI, SMU, Syracuse, Vanderbilt and Wayne State. Charm Measurements : Precise charm absolute branching ratio measurements Hadronic decays: measure strong phases Leptonic decays: decay constants f D and f D s Semi-leptonic decays: form factors V cs, V cd QCD Studies Precise measurements of quarkonia spectroscopy Searches for glue-rich exotic states Studies Beyond the Standard Model D-mixing, CP violation, rare D decays

“ZD” – Inner Drift Chamber 6 stereo layers:  r=5.3 cm – 10.5 cm  o stereo angle  |cos  < , 10 mm cells 1% X 0,.8mm Al inner tube 60:40 Helium-Propane 20  m Au-W sense wires 110  m Au-Al field wires Outer Al-mylar skin

CLEO-c Run Plan Main change for CESR to become CESR-c is the installation of 12 wigglers (6 completed, 6 more being installed). __________________________________________________ Spring and Fall 2004, we hope for 3 fb -1 at and around the  (3770). This corresponds to ~18,000,000 decays, and maybe 3,600,000 tagged D decays (310 x MARKIII, 170xBES) ____________________________________________________ Fall 2005, E=4140 MeV, we hope for 3 fb -1 giving 1,500,000 D s D s events, 300,000 tagged D s decays (480 x MARK III, 130 x BES) ___________________________________________________ Fall 2006 we may run at E=3100 MeV, 1 fb -1, giving 1,000,000,000 J/  decays (170 x MARKIII, 20 x BES II) Run plan subject to change, in particular it is dependent on the physics results from the early running.

CLEO-c Run Plan E beam (GeV) 6 CESR Wigglers installed Summer 2003 Winter 2003 took data on the  (3770),  (2S), and continuum h ~20 pb -1 continuum a ~3 pb -1  (2s) ~55 pb -1  (3770) Cross-Section Log Scale 6 Wiggler Running L ~ 5x10 31 cm -2 s -1 On target! Design Luminosity, 12 Wigglers, ~3x10 32 cm -2 s -1

Physics at the  (3770) The  (3770) is known to decay into mesons. The total cross section at E=3.77 GeV has been measured to be 26.2+/-1.0 nb (preliminary), this includes a large, and not well understood continuum component, the radiative tail of the  (2S),,and maybe some other processes as yet unexplored. Decays of the  (2S), and thus the nature of the  (2S) events at E=3770 are being investigated (see next talk). The continuum below the  (2S) is also being studied. To know how many D’s we will reconstruct, we need to know at E=3.77 GeV.

Measurement of The value of cross section is required to make predictions of the sensitivity of charm threshold e + e - experiments such as CLEO-c and BESII. Mark III (PRL (1988) with 9.4 pb -1 measured the observed cross section at GeV to be Recently BES II (Moriond '04) using 17 pb -1 measured In the BES measurement the cross section was determined using a single tag method, where the charm branching fraction to the final state under study is taken from the PDG. Here, we use a double tag method to find a value of independent of any branching fraction measurement.

General Analysis Techniques Good K-  separation by dE/dx up to 600 MeV/c For p > 600 MeV/c, RICH combined with dE/dx. K 0 s are found from two tracks with a displaced vertex.  0 ’s found from 2 gammas in the CsI To find D’s from the  (3770), we first calculate the E(D) and compare with the beam energy. If E(D)=E beam then we calculate the beam constrained mass

Measurement of at 3770 e+e+ ee K+K+  ++ K-K- Single tagged D Double tagged D e+e+ ee K+K+  ( independent on B and  in the approximation )

D 0  K  - in DD Monte Carlo M bc (GeV )  E(GeV) MC D 0 →K - π +  = 6.4 MeV MC D 0 →K - π +  = 1.6 MeV

D 0 single tag -Data M bc (GeV)  E(GeV) Luminosity = 55.81pb -1 Data D 0 →K - π +  =1.7 MeV S =9460 Require –40 MeV <  E < 30 MeV Data D 0 →K - π +  =8.2 MeV

Double Tag Monte Carlo M 1 (GeV) We search for events where the AND We use a scatter plot of two beam constrained masses to measure the double tag efficiency. MC Double tag  2 =34.8% M 2 (GeV) We find the double tag efficiency is the square of single tag efficiency with an uncertainty of 3% for

D 0 Double Tags – Data DATA Double tag Signal =102±11  (ee →D 0 D 0 )=(3.93  0.42(stat)  0.23(syst)) nb M 1 (GeV) M 2 (GeV)

D + Single Tags -Data M bc (GeV )  E(GeV) Search for delE cut :  E (-31MeV,25MeV) Data D - →K - π + π + S=13950 ±132 Data D - →K - π + π +

D + Double Tags - Data  (e + e - →D + D - )=(2.58  0.15(stat)  0.16(syst))nb Double tags Signal=338 ±19 Use the Decays M 1 (GeV) M 2 (GeV)

Summary for  (DD) Our result, which is independent of charm branching ratios, is in agreement with the BES. The BES experiment used a single tag method which depends on the PDG values for the branching fractions. The largest systematic uncertainty arises from the luminosity measurement All CLEO-c numbers are preliminary!  (D + D - )(nb) (stat.err)(sys.err)  (D 0 D 0 )(nb) (stat.err)(sys.err)  (DD) (nb) (stat.err)(sys.err)  (D + D - )/  (D 0 D 0 ) CLEO-c 2.58  0.15   0.42   0.44  BES 2.52  0.07   0.09   0.11  MARK III 2.1   

D-Tagging An initial D state can be tagged by the “other-side” D Several good tagging decay modes  Many large branching fractions  High reconstruction efficiency Net tagging efficiency ~20% Expectations from full dataset: 3,600,000 D’s Tagging can be used to find absolute branching fractions of not only hadronic decays, but semi-leptonic and even purely leptonic decays.

Measurement of In the decay of a scalar meson, M, into a lepton plus neutrino, the width is given by: We know the D + lifetime, thus a measurement of this branching fraction can give a model-free measurement of f D, This is of vital check of LQCD, and can be used to extrapolate to f B, which can enhance our understanding of B decays.

4 More D + Modes K s  + ~ 1800 events K s  +  +  0 ~ 4300 events K s  +  0 ~ 2800 events K s  +  -  + ~ 3700 events

Reconstruct one of the two D’s in a hadronic decay channel. Make use of the neutrino MM 2 observable to separate signal and background: Muon candidate consistent with minimum ionizing particle, deposited energy < 0.4 GeV in the CsI. (Too low a momentum for the muon detector). Overview of the technique

MM 2 Distribution Signal region K0p-K0p- Candidates/0.01 GeV 2 MC DATA Preliminary! ~55 pb -1 Signal Region Data Preliminary Signal Region K0K0

Backgrounds D  Background: D +   +  0 : Used max. shower energy cut. D +  K 0  + : No reconstructed K 0. D +   0  + : negligibly small, higher MM 2. D +   + : negligibly small, higher MM 2. D 0 D 0 Background: D 0 D 0 can look like D + D - : ex: D 0  K -  +, D 0   +  - Continuum Background Estimated backgrounds from MC #Tagsp+p0p+p0 K0 p+K0 p+ D0D0D0D0 Cont      0.17

Signal 9 events within 2  (-0.056<MM 2 <0.056 GeV 2 ) 0.67  0.24 estimated background events. SIGNIFICANT SIGNAL! Reconstruction efficiency ~70% B = Signal / (Tags x Efficiency) PRELIMINARY! Statistically Limited! Soon we will have 60 x the dataset! Systematic errors on B estimated to be: a)  detection efficiency (5%) b) background, taken as 100% uncertainty (7.4%) c) D + sample size (1%)

Inclusive Electron Spectrum from D Semi-Leptonic Decays Electron identification, optimized by studying radiative Bhabha events, a combination of E/p in the CsI calorimeter, dE/dx and RICH information. Object: To make improved measurements of the shape of the lepton spectra in This, leads to measurements of the semi-leptonic branching fractions.

D Meson Samples  (3770) DD D 0 D 0 tagged D + D - D + tagged X e -  Charge conjugate mode K -      K- K-  Only use one mode for each state now, more will be added later

Statistical Uncertainty ~0.5% PDG: BR = (6.75  0.29)% Statistical Uncertainty ~ 0.6% PDG: BR = (17.2  1.9)% DATA Electron Momentum (GeV/c) from D  Electron Momentum (GeV/c) from D  Number Of event /(50MeV/c ) DATA The Corrected Electron Spectra Systematic Uncertainties not Fully Evaluated The dataset should increase by a factor of 60! PRELIMINARY!

Exclusive Semi-Leptonic Decays of D’s Measurements of the absolute branching fractions for semi-leptonic decays in the D system provide: a) A stringent test of theoretical form factor models b) Input calibration of LQCD c) Direct Measurements of V cs and V cd d) Input of semi-leptonic form factor models in the B system, and thus V ub Method a) Reconstruct as many D’s as possible (62K D 0 and 30K D + Tags) b) Identify the remaining tracks in the event and define the parameter U=E miss -|P miss | and look for a peak at zero.

Excess of around 100 events in data ALL PRELIMINARY! MC (prelim) Data (prelim)

Excess of around 1.1K events ALL PRELIMINARY! MC (prelim) Data (prelim)

ALL PRELIMINARY! Other D 0 Semileptonic Modes Excess ~ 80 events Excess ~120 events. Excess ~ 25 events First Observation of this Mode! Data (prelim) Data (prelim) Data (prelim) Signals are inclusive of non-resonant contributions

D + Semileptonic Modes (1) Excess of around 400 events Excess of around 300 events The nonresonant contribution is included in the yield Excess of around 50 events ALL PRELIMINARY! Data (prelim) Data (prelim) Data (prelim)

D + semileptonic modes (2) Excess of around 35 signal events The nonresonant contribution is included in the yield A Hint of a Signal ALL PRELIMINARY! Data (prelim) Data (prelim)

The CLEO-c Reach for Semi-Leptonics The 55/pb data sample collected in fall-2003/winter-2004 by the CLEO-c detector already allows measurements of BRs for most or all of the modes considered today with statistical uncertainties comparable or smaller than those in PDG CLEO-c is expected to collect 60 times more (~3/fb) data on  (3770) as well as ~3/fb of data at E cm ~ 4140 MeV for studies of D s mesons in the coming 2 years. The CLEO-c data will dramatically improve knowledge of the BRs of charm mesons:

Summary and Conclusions The CLEO-c Detector is working well, and has accumulated ~55fb -1 at the  (3770), together with data at the  (2S) and continuum below the  (2S) With this dataset, we have new preliminary results for the cross section at the  (3770) of  (D + D - ) = 2.58  0.15  0.16 nb and  (D 0 D 0 ) = 3.93  0.42  0.23 nb We have new preliminary results for the branching fraction of the purely leptonic mode of We hope to collect 60 times more data on the  (3770) and then same amount of data at E cm ~ 4140 MeV. These data samples will play an extremely important role in particle physics, making the definitive measurements of charm hadronic, semi-leptonic and leptonic decays. These will validate and calibrate data for LQCD, and increase the physics potential of B-factories and other experiments. CLEO-c running resumes in September.