CDF Data Research Articles

STUDY OF JET ENERGY RESOLUTION AT CDF

The jet energy resolution comes from many sources, which can be grouped into two categories: (1) detector effects such as calorimeter resolution, and (2) physics effects such as fluctuations in the energy outside a clustering cone. For the detector resolution we used both CDF detector simulation and data. For the first time the full granularity of the CDF detector is used to perform corrections at "tower level" rather than at "jet level". The track momenta measured by the Central Tracking Chamber and the neutral cluster energies measured by the Central Shower Max are used to correct the calorimeter tower energies. When tested on γ + jet data, our new algorithm has shown an improvement on the jet energy resolution better than 20% compared to the standard CDF jet corrections.

Polarizations ofJ/ψandψ′in Hadroproduction at the Tevatron in thektFactorization Approach

We present a calculation for the polarizations of $J/\psi$ and $\psi'$ produced in the hadron collisions at the Fermilab Tevatron. Various color octet channels including ${}^1S_0^{(8)}$, ${}^3P_J^{(8)}$, and ${}^3S_1^{(8)}$ as well as contributions from $\chi_{cJ}$ decays are considered in the $k_t$ factorization approach. We find that in a rather wide range of the transverse momenta of $J/\psi$ and $\psi'$, the production rates could be dominated by the ${}^1S_0^{(8)}$ channel, and the predicted polarizations from the ${}^1S_0^{(8)}$ channel and $\chi_{cJ}$ feeddown contributions are roughly compatible with the preliminary CDF data. This might provide a possible release from the conflict between the NRQCD collinear parton model calculations and the CDF data.

Results from bottomonia production at the Tevatron and prospects for the LHC

We extend our previous analysis on inclusive heavy quarkonia hadroproduction to the whole Upsilon(nS) (n=1,2,3) resonance family. We use a Monte Carlo framework with the colour-octet mechanism implemented in the PYTHIA event generator. We include in our study higher order QCD effects such as initial-state emission of gluons and Altarelli-Parisi evolution of final-state gluons. We extract some NRQCD colour-octet matrix elements relevant for Upsilon(nS) (n=1,2,3) hadroproduction from CDF data at the Fermilab Tevatron. Then we extrapolate to LHC energies to predict prompt bottomonia production rates. Finally, we examine the prospect to probe the gluon density in protons from heavy quarkonia inclusive hadroproduction at high transverse momentum and its feasibility in LHC general-purpose experiments.

Nonrelativistic QCD analysis of bottomonium production at the Fermilab Tevatron

Recent data from the CDF collaboration on the production of spin-triplet bottomonium states at the Tevatron p \bar p collider are analyzed within the NRQCD factorization formalism. The color-singlet matrix elements are determined from electromagnetic decays and from potential models. The color-octet matrix elements are determined by fitting the CDF data on the cross sections for Upsilon(1S), Upsilon(2S), and Upsilon(3S) at large p_T and the fractions of Upsilon(1S) coming from chi_b(1P) and chi_b(2P). We use the resulting matrix elements to predict the cross sections at the Tevatron for the spin-singlet states eta_b(nS) and h_b(nP). We argue that eta_b(1S) should be observable in Run II through the decay eta_b -> J/psi + J/psi.

Soft gluon resummation in transverse momentum space for electroweak boson production at hadron colliders

The distribution of W and Z bosons produced with small transverse momentum ( $p_{\rm T}$ ) at hadron colliders receives important contributions from large logarithms arising from soft gluon emission. Although conventionally the all-orders resummation of these ‘Sudakov’ logarithms is performed in impact parameter (Fourier transform) space, $p_{\rm T}$ -space resummation is also possible, and offers certain advantages. We present a detailed phenomenological analysis of W and Z production at small $p_{\rm T}$ at the Tevatron $p \bar p$ collider, using $p_{\rm T}$ -space resummation. A good description of the CDF and D0 data can be obtained provided a significant non-perturbative contribution is included. We also present predictions for the LHC.

Polarization ofΥ(nS)at the Fermilab Tevatron

The polarization of inclusive {Upsilon}(nS) at the Fermilab Tevatron is calculated within the nonrelativistic QCD factorization framework. We use a recent determination of the NRQCD matrix elements from fitting the CDF data on bottomonium production from run IB of the Tevatron. The result for the polarization of {Upsilon}(1S) integrated over the transverse momentum bin 8<p{sub T}<20 GeV is consistent with a recent measurement by the CDF Collaboration. The transverse polarization of {Upsilon}(1S) is predicted to increase steadily for p{sub T} greater than about 10 GeV. The {Upsilon}(2S) and {Upsilon}(3S) are predicted to have significantly larger transverse polarizations than {Upsilon}(1S).

Bottomonia hadroproduction

We analyze Tevatron data of bottomonium hadroproduction in the framework of the colour-octet model (COM) implemented in the event generator PYTHIA [1] using CTEQ4L PDF taking into account initial-state radiation of gluons and Altarelli-Parisi evolution of final-state gluons. We obtain new values for the colour-octet matrix elements (Me's) relevant to this production process for the γ( nS) family (n=1,2,3), finding that 1 S 0 (8) + 3 P J (8) contributions are not needed in the fit. We show the different contributions to γ(1 S) production at Tevatron for P T > 8 GeV, comparing them with CDF data. Remarkably we find a quite small contribution (compatible with zero) from feeddown of χ bJ states produced through the colour-octet mechanism: γ(1 S) indirect production via χ bJ decays should be mainly ascribed to the colour-singlet model. Finally we extrapolate to LHC energies to predict γ( nS) production rates.

QCD analysis of the diffractive structure functionF2D(3)

The proton diffractive structure function $F_2^{D(3)}$ measured in the H1 and ZEUS experiments at HERA is analyzed in terms of both Regge phenomenology and perturbative QCD evolution. A new method determines the values of the Regge intercepts in ``hard'' diffraction, confirming a higher value of the Pomeron intercept than for soft physics. The data are well described by a QCD analysis in which point-like parton distributions, evolving according to the DGLAP equations, are assigned to the leading and sub-leading Regge exchanges. The gluon distributions are found to be quite different for H1 and ZEUS. A {\it global fit} analysis, where a higher twist component is taken from models, allows us to use data in the whole available range in diffractive mass and gives a stable answer for the leading twist contribution. We give sets of quark and gluon parton distributions for the Pomeron, and predictions for the charm and the longitudinal proton diffractive structure function from the QCD fit. An extrapolation to the Tevatron range is compared with CDF data on single diffraction. Conclusions on factorization breaking depend critically whether H1 (strong violation) or ZEUS (compatibility at low $\beta$) fits are taken into account.

Formula omitted] production: Tevatron and fixed-target collisions

In this talk I show the results of a fit of the NRQCD matrix elements to the CDF data for direct J ψ production, by including the radiative corrections to the gg → 3 S 1 [1] g channel and the effect of the k T -smearing. Furthermore I perform the NLO NRQCD analysis of J gy production in fixed-target proton-nucleon collisions and I fit the colour-octet matrix elements to the available experimental data. The results are compared to the Tevatron ones.

Vector boson transverse momentum distributionsat the Tevatron

We show vector boson transverse momentum distributions at the Tevatronobtained by running the HERWIGMonte Carlo event generator with matrix-element corrections.We compare our results with some recent D0 and CDF data.

Bc meson production at the Tevatron revisited

CDF recently measured the quantity σ(B c +) σ(B +) BR(B c +→J/ψℓ +ν) BR(B +→J/ψK +) , from which we determine the ratio σ(B c +) σ( b ̄ ) to be (2.08 +1.06 −0.95)×10 −3. In this note, we show that the ratio σ(B c +) σ( b ̄ ) obtained by dividing the σ( B c +) by the leading order σ( b ̄ ) is consistent with this derived CDF measurement. We calculate the cross section σ( B c +) using the perturbative QCD fragmentation functions of Braaten, Cheung, and Yuan and the corresponding induced gluon fragmentation functions, with the charm-quark mass m c as a parameter. We also estimate the parameter m c from the CDF data and then predict the production rate at RunII.

InclusiveJ/ψandψ(2S)production fromBdecay inpp¯collisions

Using information on B-meson fragmentation functions from CERN LEP 1 and adopting the nonrelativistic QCD factorization formalism proposed by Bodwin, Braaten, and Lepage, we predict the transverse-momentum distribution of J/psi mesons originating from the inclusive decays of b hadrons produced in p p-bar collisions at the Fermilab Tevatron. We determine the relevant colour-octet charmonium matrix elements from fits to CDF data on prompt charmonium hadroproduction and to CLEO data on charmonium production from B-meson decay. Our predictions are found to agree well with recent CDF and D0 data.

Rare Decays B → Xs,dνν̄ and Bs,d → l+l- in the Multiscale Walking Technicolor Model

We calculate the contributions to the rare B-decays, B → Xs,dνν̄, and Bs,d → l+l- from the unit-charged technipions. Within the considered parameter space we find that: (a) the enhancements to the branching ratios in question can be as large as three orders of magnitude; (b) the ALEPH data of B → Xsνν̄ lead to strong mass bounds on mp1 and mp8: mp8 ⩾ 620, 475 GeV for FQ = 40 GeV and mp1 = 100, 400 GeV, respectively; (c) the CDF data of Bs → μμ̄ lead to a relatively weak limit: mp8 ⩾ 320 GeV for FQ = 40 GeV and mp1 = 200 GeV.

Measurement of the Lepton Charge Asymmetry inW-Boson Decays Produced inpp¯Collisions

We describe a measurement of the charge asymmetry of leptons from W boson decays in the rapidity range 0<|y_l|<2.5 using W --> enu, munu events from 110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. The asymmetry data constrain the ratio of d and u quark momentum distributions in the proton over the x range of 0.006 to 0.34 at Q2 \approx M_W^2. The asymmetry predictions that use parton distribution functions obtained from previously published CDF data in the central rapidity region (0.0<|y_l|<1.1) do not agree with the new data in the large rapidity region (|y_l|>1.1).

Testing anomalous Higgs couplings in triple photon production at the Tevatron collider

We derive bounds on Higgs and gauge–boson anomalous interactions using the CDF data for the process p p ̄ →γγγ+X . We use a linearly realized SU L (2)× U Y (1) invariant effective Lagrangian to describe the bosonic sector of the Standard Model, keeping the fermionic couplings unchanged. All dimension–six operators that lead to anomalous Higgs interactions involving γ and Z are considered. We also show the sensitivity that can be achieved for these couplings at Fermilab Tevatron upgrades.

Production of jets at the tevatron

Measurements of the inclusive jet cross section and the dijet angular distribution using data from the Tevatron are presented. Comparisons to NLO QCD show good agreement below 250 GeV, but CDF data show an excess at higher E T ; qualitative agreement is seen between the CDF and DØ cross sections. Analysis of the dijet angular distributions exclude quark compositeness below 2.1 TeV.

Measurement of inelastic J/ $\psi$ photoproduction at HERA

We present a measurement of the inelastic, non diffractive J/$\psi$ photoproduction cross section in the reaction $e^{+} p \to e^{+} {J}/\psi X$ with the ZEUS detector at HERA. The J/$\psi$ was identified using both the $\mu^{+}\mu^{-}$ and $e^{+}e^{-}$ decay channels and events were selected within the range $0.4<z<0.9$ ($0.5<z<0.9$) for the muon (electron) decay mode, where $z$ is the fraction of the photon energy carried by the J/$\psi$ in the proton rest frame. The cross section, the $p^2_T$ and the $z$ distributions, after having subtracted the contributions from resolved photon and diffractive proton dissociative processes, are given for the photon-proton centre of mass energy range $50<W<180$ GeV; $p^2_T$ is the square of the J/$\psi$ transverse momentum with respect to the incoming proton beam direction. In the kinematic range $0.4 < z < 0.9$ and $p^2_T > 1$ GeV$^2$, NLO calculations of the photon-gluon fusion process based on the colour-singlet model are in good agreement with the data. The predictions of a specific leading order colour-octet model, as formulated to describe the CDF data on J/$\psi$ hadroproduction, are not consistent with the data.

W + 1 jet to W + 0 jet ratio at the Tevatron: a hint of new physics?

We interpret the reported disagreement between the measured ratio, R_{10}, of the W + 1 jet cross-section to the W + 0 jet cross-section at the Tevatron and the Standard Model (SM) prediction, as the effect of interactions mediated by a colour-octet analogue of the W-boson, the W_8. The presence of a W_8 with mass O(300) GeV, and with couplings to quarks and gluons of the order of electroweak strength, allows the observations of the D0 collaboration to be reproduced quite accurately. Such an interaction is not in contradiction with the present CDF data on W+ W- or dijet production, though higher luminosities may reveal measurable effects.

Light gluino and Tevatron dijet angular distributions

Abstract We consider the effects of a light gluino on the dijet angular distributions in p p collisions at s =1800 GeV . We show that the slower running of αs and the production q q ,gg → g g do not significantly alter the normalized differential cross-sections. On the other hand, single u , d squard production qg → q g with subsequent q → q g results in dijets whose angular distributions are dramatically different from that in SM. The CDF data on dijet angular distributions with integrated luminosity of 106 pb−1 exclude u and d squarks in the mass ranges 190 ≤ m ≤ 650 and 200 ≤ m ≤ 630 GeV, respectively. We extend our analysis to lower energies and show that in a future experimental analysis for dijet mass below 240 GeV squarks will be observed or ruled out.

Isolated photons at hadron colliders at O( ααs2) (I): Spin-averaged case

The cross sections for isolated and non-isolated prompt photon production with unpolarized hadron beams are studied at order αα s 2. Two methods of performing the calculations are compared. One uses purely analytic techniques and the second uses a combination of analytic and Monte Carlo techniques to perform the phase-space integrations. The results of the analytic and Monte Carlo methods are compared both before and after isolation cuts are placed on the photon. Fragmentation contributions are included at next-to-leading order in the analytic case, and the question of the infrared sensitivity of this contribution once isolation is implemented is addressed. Numerical results are presented and compared with the latest CDF data for p p → γ + X using the latest parton densities for the proton.