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04/1875 CLNS The CLEO-c Research Program University of Pittsburgh, Department of Physics and Astronomy, 3951 O'Hara St, Pittsburgh PA, 15260, USA David Asner - for the CLEO collaboration The CLEO-c research program will include studies of leptonic, semileptonic and hadronic charm decays, searches for exotic and gluonic matter, and test for physics beyond the Standard Model. The experiment and the CESR accelerator were modi ed to e ciently operate at center-of-mass energies between 3 and 5 GeV. Data at the (3770) resonance were recorded with the CLEO-c detector in September 2003 beginning a new era in the exploration of the charm sector. 1 Introduction The CLEO-c physics program 1 includes a variety of measurements that will improve the understanding of Standard Model processes as well as provide the opportunity to probe physics that lies beyond the Standard Model. The primary components of this program are measurement of absolute branching ratios for charm mesons with a precision of the order of 1 2%, determination of charm meson decay constants and of the CKM matrix elements j V j and j V j at the 1 2% level and investigation of processes in charm decays that are highly suppressed within the Standard Model. A 10 nb cross section for e+ e ! DD is assumed throughout ref. 1 . ps Since 2003, the CESR accelerator has operated 3100 MeV (J= ). energies corresponding at p p at center-of-mass The design luminosity to 3770 MeV ( 00 ), s 4140 MeV and s these energies ranges from 5 1032 cm 2 s 1 down to about 1 1032 cm 2 s 1 yielding 3 fb 1 each p at the 00 and at s 4140 MeV above D D threshold and 1 fb 1 at the J= . These integrated luminosities correspond to samples of 1.5 million D D pairs, 30 million DD pairs and one billion J= decays 1 . These datasets will exceed those of the BESII (Mark III) experiment by factors of 130 (480), 110 (310) and 20 (170), respectively. Additionally, CLEO-c has much better photon energy resolution and particle identi cation than the BESII and Mark III experiments. From fall 2001 to spring 2003 CLEO collected a total of 4 fb 1 of data on the (1S), (2S), (3S) and (5S) which is currently under analysis. These data samples will increase cs cd s s s s Resonance (3100) Table 1: The 3-year CLEO-c run plan 1 p(3770) MeV s 4140 Anticipated Reconstructed Luminosity Events 3 fb 3 fb 1 fb 1 1 1 s s 30M DD 1.5M D D 60M radiative J= the available bb bound state data by more than an order of magnitude. Only modest hardware modi cations are required for low energy operation. The transverse cooling of the CESR beams will be enhanced by 16 meters of superconducting wiggler magnets. Half of the full complement of 12 wigglers were installed in summer 2003 with the additional 6 wigglers scheduled for installation in 2004. The CLEO III silicon vertex detector was replaced by a small, low mass inner drift chamber. The solenoidal eld was reduced from 1.5 T to 1.0 T. No other modi cations are planned. Prior to the installation of the nal 6 wigglers, CLEO has accumulated 60.3 pb 1 at (3770), 3.1 pb 1 at (2S), and 21.0 pb 1 of continuum data at ps = 3:67 GeV with the new detector con guration. 2 Physics Program The following sections will outline the CLEO-c physics program. The rst section will focus on the Upsilon spectroscopy, the second section will describe the charm decay program, the third section will give an overview about the exotic and gluonic matter studies and the last section will descibe the oportunities to probe physics beyond the Standard Model. 2.1 Upsilon Spectroscopy The only established bb states below B B threshold are the three vector triplet resonances (3 S1 ) and the six and 0 (two triplets of 3 P ) that are accessible from these parent vectors via E1 radiative transitions. CLEO will address a variety of outstanding physics issues with the data samples at the (1S), (2S) and (3S), Searches for the and h : Most present theories 2 indicate the best search method for the is the hindered M1 transition from the (3S), with which CLEO might have a signal of 5 signi cance in 1 fb 1 of data. In the case of the h , CLEO established an upper limit of B( (3S) ! + h ) < 0.18% at 90% con dence level 3 . This result, based on 110 pb 1, tests some theoretical predictions 4;5;6 for this transition which range from < 0:01 1:0%. Observation of 13 D states: The bb system is unique as it has states with L = 2 that lie below the open- avor threshold. These states have been of considerable theoretical interest, as indicated by many predictions of the center-of-gravity of the triplet and by a recent review 7 . In an analysis of the (3S) CLEO data sample the (13 D2 ) state could already be observed in the four-photon cascade (3S) ! 1 0 ! 1 2 (3 D ) ! 1 2 3 ! 1 2 3 4 `+ ` . The mass of the (13 D2 ) state is determined to be 10161:1 0:6 1:6 MeV/c2 8 . Observation of New Hadronic Decays: Previously, the only hadronic decays of bottomonia experimentally observed were the transitions among vector bottomonium states 3 . In an analysis of the (3S) CLEO data sample the transitions (3S) ! (2P )1;2 ! (! (1S)) ! ( + 0 )(`+ ` ) have been observed. The branching ratios B( ! ! (1S)) and B( ! ! (1S)) are (1:63+0:35+0:16)% and (1:10+0:32+0:11 )%, respectively and the ratio of branching ratios 0:31 0:15 0:28 0:10 is determined to be 0:67+0:30 8 . 0:22 Glueball candidates in radiative (1S) decays: Signals for glueball candidates in radiative J= decay - a glue-rich environment - might be observed in radiative (1S) decays. Naively one b b J b b b b b J b J b b b1 b2 would expect the exclusive radiative decay to be suppressed in decay by a factor of roughly 40, which implies product branching fractions for radiative decay of 10 6 . With 1 fb 1 of data and e ciencies of around 30% one can expect 10 events in each of the exclusive channels, which would be an important con rmation of the J= studies. 2.2 Charm Decays The observable properties of the charm mesons are determined by the strong and weak interactions. As a result, charm mesons can be used as a laboratory for the studies of these two fundamental forces. Threshold charm experiments permit a series of measurements that enable direct study of the weak interactions of the charm quark, as well as tests of our theoretical technology for handling the strong interactions. Leptonic Charm Decays: Measurements of leptonic decays in CLEO-c will bene t from p the fully tagged D+ and D decays available at the (3770) and at s 4140 MeV. The leptonic decays D ! are detected in tagged events by observing a single charged track of the correct sign, missing energy, and a complete accounting of the residual energy in the calorimeter. The clear de nition of the initial state, the cleanliness of the tag reconstruction, and the absence of additional fragmentation tracks make this measurement straightforward and essentially background-free. This will enable measurements of the poorly known leptonic decay rates for D+ and D+ to a precision of 3 - 4% and will allow the validation of theoretical calculations of the decay constants f and f s at the 1 - 2 % level. Table 2 summarizes the expected precision in the decay constant measurements. s s s D D Table 2: Expected decay constants errors for leptonic decay modes Decay Constant Error % Decay Mode PDG 2000 CLEO-c D! (f ) Upper Limit 2.3 (f ) 17 1.7 D! (f ) 33 1.6 D! 1 + + s + + D s + + Ds Ds measurements in the charm sector against which the theoretical tools needed to extract CKM matrix information precisely from heavy quark decay measurements will be tested and calibrated. CLEO-c will measure the branching ratios of many exclusive semileptonic modes, including D0 ! K e+ , D0 ! e+ , D0 ! K e+ , D+ ! K 0 e+ , D+ ! 0 e+ , D+ ! K 0 e+ , D+ ! e+ and D+ ! K 0 e+ . The measurement in each case is based on the use of tagged events where the cleanliness of the environment provides nearly background-free signal samples, and will lead to the determination of the CKM matrix elements j V j and j V j with a precision level of 1.6% and 1.7%, respectively. Measurements of the vector and axial vector form factors V (q2 ), A1 (q2 ) and A2 (q2 ) will also be possible at the 5% level. Table 3 summarizes the expected fractional error on the branching ratios. s s cs cd Semileptonic Charm Decays: The CLEO-c program will provide a large set of precision Table 3: Expected branching fractional errors for selected semileptonic decay modes BR fractional error % Decay Mode PDG 2000 CLEO-c D ! K` 5 0.4 D!` 16 1.0 D!` 48 2.0 D!` 25 3.1 1 0 0 + s HQET provides a successful description of the lifetimes of charm hadrons and of the absolute semileptonic branching ratios of the D0 and D 9 . Isospin invariance in the strong forces implies (D0 ) ' (D+ ) up to corrections of O(tan2 ) ' 0:05. Likewise, SU(3) symmetry 0 relates (D ) and (D+ ), but a priori would allow them to di er by as much as 30%. However, HQET suggests that they should agree to within a few percent. The charm threshold region is the best place to measure absolute inclusive semileptonic charm branching ratios, in particular B(D ! X` ) and thus (D ). Implications for CKM Triangle: The CLEO-c program of leptonic and semileptonic measurements has two components: one of calibrating and validating theoretical methods for calculating hadronic matrix elements, which can then be applied to all problems in CKM extraction in heavy quark physics; and one of extracting CKM elements directly from the CLEO-c data. The direct results of CLEO-c are the precise determination of j V j, j V j, f , f s , and the semileptonic form factors. The precision knowledge of the decay constants f and f s , together with the rigorous calibration of theoretical techniques for calculating heavy-to-light semileptonic form factors, are for required the direct extraction of CKM elements from CLEO-c. This also drives the indirect results, namely the precision extraction of CKM elements from experimental measurements of the B mixing frequency, the B mixing frequency, and the B ! ` decay rate measurements which will be performed by BaBar, Belle, CDF, D0, BTeV, LHCb, ATLAS and CMS. In Table 4 the combined projections are presented 1 . In the determination of the CKM elements j V j and j V j from B and B mixing j V j= 1 is used. The tabulation also includes improvement in the direct measurement of j V j expected from the Tevatron experiments 10 . s SL SL C Fl SL SL s s SL s cd cs D D D D d s cd cs s tb tb Present Knowledge ! After CLEO-c V =V = 0.1% ! 0.1% V =V = 1% ! 1% V =V = 25% ! 5% V =V = 7% ! 1% V =V = 16% ! 1% V =V = 5% ! 3% V =V = 36% ! 5% V =V = 39% ! 5% V =V = 29% ! 15% ud ud us us ub ub cd cd cs cs cb cb td td ts ts tb tb Table 4: CKM elements at present and after CLEO-c 1 Hadronic Charm Decays: The CLEO and ALEPH experiments by far provide the most precise measurements for the decay D ! K . They use the same technique by looking at D ! D decays and taking the ratio of the D decays into K to the number of decays 0 + + + 0 0 + + + with only the from the D decay detected. The dominant systematic uncertainty is the background level in the latter sample. In both experiments, the systematic errors exceed the statistical errors. The D+ absolute branching ratios are determined by using fully reconstructed Table 5: Expected branching fractional errors for hadronic decay modes 1 BR fractional error % Decay Mode PDG 2000 CLEO-c D !K 2.4 0.6 D !K 7.2 0.7 D! 25 1.9 1 0 + s dominant systematic uncertainty is due to the background shape in the partially reconstructed sample. By reconstructing both D mesons in DD decays, the background can be reduced to almost zero and the branching ratio fractional error can be improved signi cantly (see Table 5). D0 and using isospin symmetry. Hence, this rate cannot be determined any better than the absolute D0 decay rate using this technique. The D+ absolute branching ratios are determined by comparing fully reconstructed B ! D( ) D + to the partially reconstructed B ! D( ) D + requiring only the from the D + decay. Here the + s s s s D + decays, comparing 0 D+ with 2.3 Exotic and Gluonic Matter The approximately one billion J= produced at CLEO-c will be a glue factory to search for glueballs and other glue-rich states via J= ! gg ! X decays. The region of 1 < M < 3 GeV/c2 will be explored with partial wave analyses for evidence of scalar or tensor glueballs, glueball-qq mixtures, exotic quantum numbers, quark-glue hybrids and other new forms of matter predicted by QCD. This includes the establishment of masses, widths, spin-parity quantum numbers, decay modes and production mechanisms for any identi ed states, a detailed exploration of reported glueball candidates such as the scalar states f0 (1370), f0 (1500) and f0 (1710), and the examination of the inclusive photon spectrum J= ! X with < 20 MeV photon resolution and identi cation of states with up to 100 MeV width and inclusive branching ratios above 1 10 4 . In addition, spectroscopic searches for new states of the bb system and for exotic hybrid states such as cgc will be made using the 4 fb 1 (1S), (2S), (3S) and (5S) data. Analysis of (1S) ! X will play an important role in verifying any glueball candidates found in the J= data. X 2.4 Charm Beyond the Standard Model CLEO-c has the opportunity to probe for physics beyond the Standard Model. Three highlights - rare charm decays, D0 D0 -mixing and CP violation - are discussed in the following sections. Rare Charm Decays: Rare decays of charmed mesons and baryons provide \background-free" probes of new physics e ects. In the framework of the Standard Model (SM) these processes occur only at one loop level. SM predicts vanishingly small branching ratios for processes such as D ! =K ( ) `+` due to the almost perfect GIM cancellation between the contributions of strange and down quarks. This causes the SM predictions for these transitions to be very uncertain. In addition, in many cases annihilation topologies also give sizable contribution. Several model-dependent estimates exist indicating that the SM predictions for these processes are still far below current experimental sensitivities 11;12 . D0 D0 Mixing: Neutral avor oscillation in the D meson system is highly suppressed within the Standard Model. The time evolution of a particle produced as a D0 or D0 , in the limit of CP conservation, is governed by four parameters: x = m= , y = =2 characterize the mixing matrix, the relative strong phase between Cabibbo favored (CF) and doubly-Cabibbo suppressed (DCS) amplitudes and R the DCS decay rate relative to the CF decay rate 13 . Standard Model based predictions for x and y, as well as a variety of non-Standard Model expectations, span several orders of magnitude 14 . It is reasonable to assume that x y 10 3 in the Standard Model. The mass and width di erences x and y can be measured in a variety of ways. The most precise limits are obtained by exploiting the time-dependence of D decays 13 . Time-dependent analyses are not feasible at CLEO-c; however, the quantum-coherent 0:05 1;15 . D0 D0 state provides time-integrated sensitivity to x, y at O(1%) level and cos Although CLEO-c does not have su cient sensitivity to observe Standard Model charm mixing the projected results compare favorably with current experimental results; see Fig. 1 in Ref. 13 . CP Violation: Theoretical predictions for the rate of CP violation in the Standard Model have signi cant uncertainties. Standard Model predictions for the rate of CP violation in charm mesons are as large as 0.1% for D0 decays and as large as 1% for certain D+ and D+ decays 16 . The process e+ e ! (3770) ! D0 D0 produces an eigenstate of CP+, in the rst step, since the (3770) has J equal to 1 . Now consider the case where both the D0 and the D0 decay into CP eigenstates. Then the decays (3770) ! f+ f+ or f f are forbidden, where f+ denotes a CP+ eigenstate and f denotes a CP eigenstate. This is because CP(f f ) = ( 1) = 1 for the ` = 1 (3770). Hence, if a nal state such as (K + K )( + ) is observed, one immediately has evidence of CP violation. Moreover, all CP+ and CP eigenstates can be summed over for this measurement. The expected sensitivity to direct CP violation is 1%. D s PC i j i j i j ` This measurement can also be performed at higher energies where the nal state D 0 D 0 is produced. When either D decays into a 0 and a D0 , the situation is the same as above. When the decay is D 0 ! D0 the CP parity is changed by a multiplicative factor of -1 and all decays f+ f violate CP 17 . Additionally, CP asymmetries in CP even initial states depend linearly on x allowing sensitivity to CP violation in mixing of 3% 1 . Dalitz Plot Analyses: A Dalitz plot analysis of multibody nal states measures amplitudes and phases rather than the rates and so may provide greater sensitivity to CP violation. In the limit of CP conservation, charge conjugate decays will have the same Dalitz distribution. Although the D+ and D+ decays are self-tagging, there have been no reported Dalitz analyses that search for CP violation with charged D's. The decay D0 ! K + proceed through intermediate states that are CP+ eigenstates, such as K f0 , CP such as K and avor eigenstates such as K + 18 . It is noteworthy that for uncorrelated D0 the interference between CP+ and CP eigenstates integrates to zero across the Dalitz plot but for correlated D the interference between CP+ and CP eigenstates is locally zero. The Dalitz plots for (3770) ! D0 D0 ! f+ K + and (3770) ! D0D0 ! f K + will be distinct and the Dalitz plot for the untagged sample (3770) ! D0 D0 ! XK + will be distinct from that observed with uncorrelated D's from continuum production at 10 GeV 18 . The sensitivity at CLEO-c to CP violation with Dalitz plot analyses has not yet been evaluated. i j s S S S S S S 3 Summary The high-precision charm and quarkonium data will permit a broad suite of studies of weak and strong interaction physics as well as probes of new physics. In the threshold charm sector measurements are uniquely clean and make possible the unambigous determinations of physical quantities discussed above. The advances in strong interaction calculations enabled by CLEO-c will allow advances in weak interaction physics in all heavy quark endeavors and in future explorations for physics beyond the Standard Model. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. Briere, R. A., et al., CLNS-01-1742 (2001). Godfrey, S., and Rosner, J. L., Phys. Rev., D64, 074011 (2001). Butler, F., et al., Phys. Rev., D49, 40{57 (1994). Kuang, Y.-P., and Yan, T.-M., Phys. Rev., D24, 2874 (1981). Voloshin, M. B., Sov. J. Nucl. Phys., 43, 1011 (1986). Voloshin, M. B., and Zakharov, V. I., Phys. Rev. Lett., 45, 688 (1980). Godfrey, S., and Rosner, J. L., Phys. Rev., D64, 097501 (2001). Skwarnicki, T., Proceedings of Lepton-Photon (2003). Bigi, I. I. Y., Proceedings of BCP3 (2000). Swain, J., and Taylor, L., Phys. Rev., D58, 093006 (1998). Fajfer, S., et al., Phys. Lett., B487, 81{86 (2000). Burdman, G., et al., Phys. Rev., D52, 6383{6399 (1995). Asner, D., D0 D0 Mixing in Review of Particle Physics, Phys. Lett., B592, 1 (2004). Petrov, A. A., Proceedings of Flavor Physics and CP Violation (2003). Gronau, M., Grossman, Y., and Rosner, J. L., Phys. Lett., B508, 37{43 (2001). Buccella, F., Lusignoli, M., and Pugliese, A., Phys. Lett., B379, 249{256 (1996). Bigi, I. I. Y., and Sanda, A. I., Cambridge Monogr. Part. Phys. Nucl. Phys. Cosmol., 9, p. 180 (2000). 18. Muramatsu, H., et al., Phys. Rev. Lett., 89, 251802 (2002).

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