Search Results (12 total)

We present a measurement of the mass difference m(D_s⁺)-m(D⁺), where both the D_s⁺ and D⁺ are reconstructed in the φπ⁺ decay channel. This measurement uses 11.6 pb^-1 of data collected by CDF II using the new displaced-track trigger. The mass difference is found to be m(D_s⁺)-m(D⁺)=99.41±0.38(stat)±0.21(syst) MeV/c².

The booster ionization profile monitor (IPM) obtains transverse beam profiles by measuring the distribution of ions resulting from interaction of the proton beam with background gas in the beam chamber. The challenge of the IPM operation is that the measured ion distribution is not an exact representation of the beam distribution, since the ion trajectories are influenced by the electromagnetic field of the beam. We have developed a new model for the dependence of the IPM measurement on the beam parameters, assuming a Gaussian beam distribution. Our model of the ion dynamics in the detector was constrained by making independent measurements of the horizontal beamwidth at injection and extraction and comparing these to data taken from the IPM at the same time. Our calibration results in the formula σ_measured=σ_real+C₁Nσ_real^p₁, where N is the number of protons in the machine, in units of 10¹², C₁=(1.13±0.06)×10^-5, in units of (meters)^1-p₁/10¹², and p₁=-0.615±0.013; the subscript “measured” indicates the raw IPM measurement, the subscript “real” the true beamwidth. This result is the first detailed calibration of the response of the booster IPM based on experimental data.

QCD predicts soft radiation patterns that are particularly simple for W+ jet production. We demonstrate how these patterns can be used to distinguish between the parton-level subprocesses probabilistically on an event-by-event basis. As a test of our method we demonstrate correlations between the soft radiation and the radiation inside the outgoing jet.

We study the phenomenology of fixed-target elastic J/ψ photoproduction in the nonrelativistic QCD (NRQCD) factorization formalism. Our goal is to test an essential feature of this formalism—the color-octet mechanism. We obtain an order-of-magnitude estimate for a certain linear combination of NRQCD color-octet matrix elements. Our estimate is consistent with other empirical determinations and with the v-scaling rules of NRQCD.

I calculate heavy-light decay constants in a nonrelativistic potential model. The resulting estimate of heavy quark symmetry breaking conflicts with similar estimates from lattice QCD. I show that a semirelativistic potential model eliminates the conflict. Using the results of heavy quark effective theory allows me to identify and compensate for shortcomings in the model calculations in addition to isolating the source of the differences in the two models. The results lead to a rule as to where the nonrelativistic quark model gives misleading predictions.

I present a very simple model, based on the model of Isgur, Scora, Grinstein, and Wise, which can be used to calculate the effects which appear at subleading order in heavy quark effective theory. I include both the general formalism and specific results. The formalism transparently reproduces the results of heavy quark effective theory, while giving insight into such things as the vanishing of certain form factors at zero recoil. I discuss the implications of these results for both heavy quark effective theory and the Isgur-Scora-Grinstein-Wise model.

Decay constants of D and B mesons are estimated within the framework of a heavy-quark approach using measured isospin mass splittings in the D, D^*, B, and B^* states to isolate the electromagnetic hyperfine interaction between quarks. A relation following from the use of splittings in kaons is also considered.

The decays of D mesons to Klν and K^*lν final states exhibit significant deviations from the predictions of heavy-quark symmetry, as one might expect since the strange quark's mass is of the same order as the QCD scale. Nonetheless, in order to understand where the most significant effects might lie for heavier systems (such as B→Dlν and B→D^*lν), the pattern of these deviations is analyzed from the standpoint of perturbative QCD and O(1 / m_s) corrections. Two main effects are noted. First, the perturbative QCD corrections lead to an overall decrease of predicted rates, which can be understood in terms of production of excited kaonic states. Second, O(1 / m_s) effects tend to cancel the perturbative QCD corrections in the case of Klν decay, while they have minimal effect in K^*lν decay.

Gronau and Wakaizumi have proposed a model in which the dominant b decays are due to exchange of a new right-handed gauge boson. A test of this model via the study of polarized Λ_b baryons produced in e⁺e^-→Z→Λ_b+X is suggested.

We compare the results of two sophisticated Monte Carlo simulators with published data on relativistic heavy-ion collisions. In addition, we include results of a simple Monte Carlo simulator, which is based on the gross features of the data and contains no correlations. We find that the data show a strong signal of intermittency that the three Monte Carlo simulators fail to reproduce. Furthermore, we find that the sophisticated simulators do no better than the simple one in that neither show any signal of intermittency at all.

The angles of all charged secondaries have been measured in central collisions of ¹⁶O with AgBr at 14.6, 60, and 200 GeV per nucleon. The pseudorapidity distributions are approximately Gaussian in shape. The widths increase monotonically with beam energy, but are essentially independent of multiplicity at a fixed beam energy. Quantitatively, the widths are consistent with Landau’s hydrodynamical model and inconsistent with a spherical fireball model and with Bjorken’s hydrodynamical scaling model. There are no statistically significant correlations in the azimuthal angle of the observed charged secondaries. Analysis of the two-particle pseudorapidity correlation functions and of the pseudorapidity gap distributions provide no evidence of significant cluster production. The data are consistent with a Monte Carlo simulation based on independent emission of the secondary particles, although intrinsic few-particle correlations could be hidden by the high multiplicities in these events.

The method of scaled factorial moments is used to study short-range fluctuations in the pseudorapidity distributions of particles produced in high-energy interactions in nuclear emulsion. An intermittent behavior of the fluctuations is clearly observed in both proton (200 and 800 GeV) and oxygen (60 and 200 GeV/nucleon) beam interactions in emulsion.