K. W. Edwards

Measurement of the pseudoscalar decay constant f{sub D{sub s}} using D{sub s}{sup +}{yields}{tau}{sup +}{nu}, {tau}{sup +}{yields}{rho}{sup +}{nu} decays

Analyzing 600 pb{sup -1} of e{sup +}e{sup -} collisions at 4170 MeV center-of-mass energy with the CLEO-c detector, we measure the branching fraction B(D{sub s}{sup +}{yields}{tau}{sup +}{nu})=(5.52{+-}0.57{+-}0.21)% using the {tau}{sup +}{yields}{rho}{sup +}{nu} decay mode. Combining with other CLEO measurements of B(D{sub s}{sup +}{yields}{tau}{sup +}{nu}) we determine the pseudoscalar decay constant f{sub D{sub s}}=(259.7{+-}7.8{+-}3.4) MeV consistent with the value obtained from our D{sub s}{sup +}{yields}{mu}{sup +}{nu} measurement of (257.6{+-}10.3{+-}4.3) MeV. Combining these measurements we find a value of f{sub D{sub s}}=(259.0{+-}6.2{+-}3.0) MeV, that differs from the most accurate prediction based on unquenched lattice gauge theory of (241{+-}3) MeV by 2.4 standard deviations. We also present the first measurements of B(D{sub s}{sup +}{yields}K{sup 0}{pi}{sup +}{pi}{sup 0})=(1.00{+-}0.18{+-}0.04)%, and B(D{sub s}{sup +}{yields}{pi}{sup +}{pi}{sup 0}{pi}{sup 0})=(0.65{+-}0.13{+-}0.03)%, and measure a new value for B(D{sub s}{sup +}{yields}{eta}{rho}{sup +})=(8.9{+-}0.6{+-}0.5)%.

Dalitz plot analysis of the D{sup +}{yields}K{sup -}{pi}{sup +}{pi}{sup +} decay

We perform a Dalitz plot analysis of D{sup +}{yields}K{sup -}{pi}{sup +}{pi}{sup +} decay with the CLEO-c data set of 572 pb{sup -1} of e{sup +}e{sup -} collisions accumulated at the {psi}(3770). This corresponds to 1.6x10{sup 6} D{sup +}D{sup -} pairs from which we select 140 793 candidate events with a small background of 1.1%. We compare our results with previous measurements using the isobar model. We modify the isobar model with an improved description of some of the contributing resonances and get better agreement with our data. We also consider a quasi-model-independent approach and measure the magnitude and phase of the contributing K{pi} S wave in the range of invariant masses from the threshold to the maximum in this decay. This gives an improved description of our data over the isobar model. Finally we allow for an isospin-two {pi}{sup +}{pi}{sup +} S wave contribution and find that adding this to both the isobar model and the quasi-model-independent approach gives the best description of our data.

Measurement of the Decay Constant f{sub D{sub s}{sup +}} Using D{sub s}{sup +}{yields}l{sup +}{nu}

We measure the decay constant f{sub D{sub s}{sup +}} using the D{sub s}{sup +}{yields}l{sup +}{nu} channel, where the l{sup +} designates either a {mu}{sup +} or a {tau}{sup +}, when the {tau}{sup +}{yields}{pi}{sup +}{nu}. Using both measurements we find f{sub D{sub s}{sup +}}=274{+-}13{+-}7 MeV. Combining with our previous determination of f{sub D{sup +}}, we compute the ratio f{sub D{sub s}{sup +}}/f{sub D{sup +}}=1.23{+-}0.11{+-}0.04. We compare with theoretical estimates.

Evidence for the Decay D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup -}e{sup +}{nu}{sub e}

Using a 281 pb{sup -1} data sample collected at the {psi}(3770) with the CLEO-c detector, we present the first absolute branching fraction measurement of the decay D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup -}e{sup +}{nu}{sub e} at a statistical significance of about 4.0 standard deviations. We find 10 candidates consistent with the decay D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup -}e{sup +}{nu}{sub e}. The probability that a background fluctuation accounts for this signal is less than 4.1x10{sup -5}. We find B(D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup -}e{sup +}{nu}{sub e})=[2.8{sub -1.1}{sup +1.4}(stat){+-}0.3(syst)]x10 = {sup -4}. By restricting the invariant mass of the hadronic system to be consistent with K{sub 1}(1270), we obtain the product of branching fractions B(D{sup 0}{yields}K{sub 1}{sup -}(1270)e{sup +}{nu}{sub e})xB(K{sub 1}{sup -}(1270){yields}K{sup -}{pi}{sup +}{pi}{sup -})=[2.5{sub -1.0} = {sup +1.3}(stat){+-}0.2(syst)]x10{sup -4}. Using B(K{sub 1}{sup -}(1270){yields}K{sup -}{pi}{sup +}{pi}{sup -})=(33{+-}3)%, we obtain B(D{sup 0}{yields}K{sub 1}{sup -}(1270)e{sup +}{nu}{sub e})=[7.6{sub -3.0}{sup +4.1}(stat){+-}0.6(syst){+-}0.7] = x10{sup -4}. The last error accounts for the uncertainties in the measured K{sub 1}{sup -}(1270){yields}K{sup -}{pi}{sup +}{pi}{sup -} branching fractions.