CDF Data Research Articles

RECENT THEORETICAL RESULTS IN HEAVY FLAVOUR PRODUCTION

We review one-particle inclusive production of heavy-flavored hadrons in a framework which resums the large collinear logarithms through the evolution of the FFs and PDFs and retains the full dependence on the heavy-quark mass. We focus on presenting results for the inclusive cross section for the production of charmed mesons in [Formula: see text] collisions and the comparison with CDF data as well as on inclusive B-meson production and comparison with recent CDF data, for which in both new determined fragmentation functions have been used.

Model-independent and quasi-model-independent search for new physics at CDF

Data collected in Run II of the Fermilab Tevatron are searched for indications of new electroweak scale physics. Rather than focusing on particular new physics scenarios, CDF data are analyzed for discrepancies with respect to the standard model prediction. A model-independent approach (Vista) considers the gross features of the data, and is sensitive to new large cross section physics. A quasi-model-independent approach (Sleuth) searches for a significant excess of events with large summed transverse momentum, and is particularly sensitive to new electroweak scale physics that appears predominantly in one final state. This global search for new physics in over three hundred exclusive final states in 927 pb^-1 of ppbar collisions at sqrt(s)=1.96 TeV reveals no such significant indication of physics beyond the standard model.

The THEMIS Array of Ground-based Observatories for the Study of Auroral Substorms

The NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) project is intended to investigate magnetospheric substorm phenomena, which are the manifestations of a basic instability of the magnetosphere and a dominant mechanism of plasma transport and explosive energy release. The major controversy in substorm science is the uncertainty as to whether the instability is initiated near the Earth, or in the more distant >20 Re magnetic tail. THEMIS will discriminate between the two possibilities by using five in-situ satellites and ground-based all-sky imagers and magnetometers, and inferring the propagation direction by timing the observation of the substorm initiation at multiple locations in the magnetosphere. An array of stations, consisting of 20 all-sky imagers (ASIs) and 30-plus magnetometers, has been developed and deployed in the North American continent, from Alaska to Labrador, for the broad coverage of the nightside magnetosphere. Each ground-based observatory (GBO) contains a white light imager that takes auroral images at a 3-second repetition rate (“cadence”) and a magnetometer that records the 3 axis variation of the magnetic field at 2 Hz frequency. The stations return compressed images, “thumbnails,” to two central databases: one located at UC Berkeley and the other at the University of Calgary, Canada. The full images are recorded at each station on hard drives, and these devices are physically returned to the two data centers for data copying. All data are made available for public use by scientists in “browse products,” accessible by using internet browsers or in the form of downloadable CDF data files (the “browse products” are described in detail in a later section). Twenty all-sky imager stations are installed and running at the time of this publication. An example of a substorm was observed on the 23rd of December 2006, and from the THEMIS GBO data, we found that the substorm onset brightening of the equatorward arc was a gradual process (>27 seconds), with minimal morphology changes until the arc breaks up. The breakup was timed to the nearest frame (<3 s) and located to the nearest latitude degree at about ±3oE in longitude. The data also showed that a similar breakup occurred in Alaska ∼10 minutes later, highlighting the need for an array to distinguish prime onset.

Calculation of prompt diphoton production cross sections at Fermilab Tevatron and CERN LHC energies

A fully differential calculation in perturbative quantum chromodynamics is presented for the production of massive photon pairs at hadron colliders. All next-to-leading order perturbative contributions from quark-antiquark, gluon-(anti)quark, and gluon-gluon subprocesses are included, as well as all-orders resummation of initial-state gluon radiation valid at next-to-next-to-leading logarithmic accuracy. The region of phase space is specified in which the calculation is most reliable. Good agreement is demonstrated with data from the Fermilab Tevatron, and predictions are made for more detailed tests with CDF and DO data. Predictions are shown for distributions of diphoton pairs produced at the energy of the Large Hadron Collider (LHC). Distributions of the diphoton pairs from the decay of a Higgs boson are contrasted with those produced from QCD processes at the LHC, showing that enhanced sensitivity to the signal can be obtained with judicious selection of events.

Diffractive hadroproduction ofW±andZ0bosons at high energies

Results from a phenomenological analysis of $W$ and $Z$ hard diffractive hadroproduction at high energies are reported. Using the Regge factorization approach, we consider the recent diffractive parton density functions extracted by the H1 Collaboration at DESY-HERA. In addition, we take into account multiple Pomeron exchange corrections considering a gap survival probability factor. It is found that the ratio of diffractive to nondiffractive boson production is in good agreement with the CDF and D0 data. We make predictions which could be compared to future measurements at the LHC.

First Observation of Bottom Baryon ∑b States at CDF

We present the latest results on the search for bottom baryon states ∑b using ∼ 1 fb−1 of CDF data. The study is performed with the world's largest sample of fully reconstructed Λ0b decays collected by CDF II detector at √s = 1.96 TeV in the hadronic trigger path. We observe 4 new states consistent with ∑b(*)± bottom baryons.

Search for tt̄ in the τ dilepton channels based on 350 pb−1 of CDF data

The search for the top pair production in the dilepton signature with one electron (or one muon) and one τ lepton decaying hadronically is discussed in this paper. The reported study is based on 359 pb-1 data recorded by the CDF experiment at the Tevatron (FNAL). The dominant backgrounds are due to the process Z → τlτhad, and to events with jets faking τ′s, predominantly due to the production of W → lv + jets and the QCD backgrounds. A new method is developed to estimate the τ fake rate as given by these various processes. With the statistics available in this reported study, the probability for the 2.7 ± 0.4 expected background events to give rise to the observed number (5) or more is 15%. This is roughly equivalent to a one sigma excess over the expected background, and is in good agreement with the total number of events expected from the signal and the background, namely: 5.0 ± 0.5. The work is in progress on three times more data and should lead soon to a 3σ evidence and the first experimental observation of this signal. This paper also stress the importance of this signal as an entry point for New Physics, where decays into τ leptons are predicted to be predominant.

Real time secondary vertexing at CDF

The Online Silicon Vertex Tracker (SVT) is the trigger processor dedicated to the 2-D reconstruction of charged particle trajectories at the Level 2 of the CDF trigger. As the Tevatron luminosity rises, multiple interactions increase the complexity of events and thus the SVT processing time, reducing the amount of data CDF can record. The SVT upgrade aims to increase the SVT processing power to restore at high luminosity the original CDF Data Acquisition capability. In this paper we review the tracking algorithms implemented in the SVT and we report on the first step in the SVT upgrade.

Probing a Very NarrowZ′Boson with CDF and D0 Data

The CDF and D0 data of nearly 475 pb(-1) in the dilepton channel is used to probe a recent class of models, Stueckelberg extensions of the standard model (StSM), which predict a Z' boson whose mass is of topological origin with a very narrow decay width. A Drell-Yan analysis for dilepton production via this Z' shows that the current data put constraints on the parameter space of the StSM. With a total integrated luminosity of 8 fb(-1), the very narrow can be discovered up to a mass of about 600 GeV. The StSM Z' will be very distinct since it can occur in the region where a Randall-Sundrum graviton is excluded.

Data Processing Model for the CDF Experiment

The data processing model for the CDF experiment is described. Data processing reconstructs events from parallel data streams taken with different combinations of physics event triggers and further splits the events into datasets of specialised physics interests. The design of the processing control system makes strict requirements on bookkeeping records, which trace the status of data files and event contents during processing and storage. The computing architecture was updated to meet the mass data flow of the Run II data collection, recently upgraded to a maximum rate of 40 MByte/sec. The data processing facility consists of a large cluster of Linux computers with data movement managed by the CDF data handling system to a multi-petaByte Enstore tape library. The latest processing cycle has achieved a stable speed of 35 MByte/sec (3 TByte/day). It can be readily scaled by increasing CPU and data-handling capacity as required

Pomeron structure functions from HERA to Tevatron and LHC

The proton diffractive structure function F 2 D ( 3 ) measured in the H1 and ZEUS experiments at HERA are analysed in terms of perturbative QCD in the perspective of the QCD extrapolation to the Tevatron and the LHC. It is shown that both data sets can be well described by a QCD analysis in which point-like parton distributions, evolving according to the next-leading DGLAP equations, are assigned to the leading and sub-leading Regge exchanges. For present data from H1 and ZEUS the gluon distributions are found to be quite different and we give the corresponding sets of quark and gluon parton distributions for the Pomeron, extracted from the two experiments. An extrapolation to the Tevatron range is compared with CDF data on single diffraction. Conclusions on factorization breaking between HERA and Tevatron critically depend on whether H1 (strong violation) or ZEUS (compatibility at low β) fits are taken into account. Using the double pomeron formulation in central diffractive dijet production we show that the Tevatron mass fraction is much sensitive to the high β tail of the gluon in the pomeron, suggesting a new way of handling the otherwise badly known gluon distribution in the pomeron. Extrapolation of the fits to very high Q 2 are given since they will be relevant for QCD and diffraction studies at the LHC.

Recent CDF results on heavy and exotic baryons in p-pbar collisions at [formula omitted

Since March 2001 a new period of CDF data taking (called Run II) began at the p{bar p} Tevatron collider. The upgrade of Collider Detector at Fermilab improved the tracking system: the vertexing, triggering and particle identification capabilities. This has allowed a further development of B physics, because the B{sub s} and {Lambda}{sub b} are produced in hadronic collisions. Here measurements of the mass and lifetime of {Lambda}{sub b} in two decay channels are presented. Using particle identification (PID) information from the time of flight and the dE/dx, CDF performed pentaquark searches for {Theta}{sup +}, {Xi}{sub 3/2}{sup --,0} and {Theta}{sub c}{sup 0}, following the recent interest in exotic baryon spectroscopy.

Soft colour interactions and diffractive Higgs production

The topical subject of Higgs production in diffractive hard scattering events at the Tevatron and LHC is discussed. This has been proposed as a Higgs discovery channel with appealing experimental features. Predictions are obtained from the Soft Colour Interaction model, where rapidity gaps are created by a new soft interaction added to the normal hard scattering processes, implemented in the Monte Carlo event generator PYTHIA. A brief review of the successful application of the model to describe all CDF and DO data on diffractive hard scattering, such as production of W/Z, dijets, beauty and J/psi is also given.

The pomeron in exclusive vector meson production

An earlier developed model for vector meson photoproduction, based on a dipole Pomeron exchange, is extended to electroproduction. Universality of the non linear Pomeron trajectory is tested by fitting the model to ZEUS and H1 data as well as to CDF data on $\bar pp$ elastic scattering

Pomeron in exclusive vector meson production

An earlier developed model for vector meson photoproduction, based on a dipole Pomeron exchange, is extended to electroproduction. Universality of the non linear Pomeron trajectory is tested by fitting the model to ZEUS and H1 data as well as to CDF data on $\bar pp$ elastic scattering.

The CDF silicon detector upgrade and performance

Abstract The CDF silicon tracking and vertexing system for Run2a of the Tevatron consists of eight layers, arranged in cylinders, spanning radii from 1.35 to 28 cm , and lengths from 90 cm to nearly 2 m for a total of 6 m 2 of silicon and 722,000 readout channels. This article will cover the last phase of detector assembly as well as the internal alignment of the subdetectors. The installation of the silicon into the main CDF detector, its commissioning and data taking will be discussed. First results will show signal to noise and charge collection of the ladders as well as the global alignment of the CDF drift chamber and the silicon detector with respect to each other and to the beam.

Diffractive dijet production

We explore the diffractive interaction of a proton with an antiproton which results in centrally produced dijets. This process has been recently studied at the Tevatron. We make predictions within an Ingelman–Schlein approach and compare them to the recent data presented by the CDF Collaboration. Earlier calculations resulted in theoretical cross-sections which are much larger than those observed by CDF. We find that, after consideration of hadronisation effects and the parton shower, and using parton density functions extracted from diffractive deep inelastic scattering at HERA, it is possible to explain the CDF data. We need to assume a gap survival probability of around 10% and this is in good agreement with the value predicted by theory. We also find that the non-diffractive contribution to the process is probably significant in the kinematical region probed by the Tevatron.

Recent experimental data and the size of the quark in the constituent quark model

We use the Constituent Quark Model (CQM) to describe CDF data on double parton cross section and HERA data on the $ J / \Psi$ ratio cross section of elastic and inelastic diffractive productions. Our estimate shows that the radius of the constituent quark turns out to be rather small, $R^2_{quark} \approx 0.1 Gev^{-2}$, in accordance with the assumption on which CQM is based.

Quarkonium feed-down and sequential suppression

About 40-50 % of the quarkonium ground states J/psi(1S) and Upsilon(1S) produced in hadronic collisions originate from the decay of higher excitations. In a hot medium, these higher states are dissociated at lower temperatures than the more tightly bound ground states, leading to a sequential suppression pattern. Using new finite temperature lattice results, we specify the in-medium potential between heavy quarks and determine the dissociation points of different quarkonium states. On the basis of recent CDF data on bottomonium production, we then obtain first predictions for sequential Upsilon suppression in nuclear collisions.

A Comparison of the Underlying Event in Jet and Minimum Bias Events

In order to determine more accurately the energy contribution in a jet cone due to the underlying event, and in oder to understand better the ambient event environment at both the Tevatron and the LHC, a study has been carried out in CDF of the energy distribution in a cone of radius 0.7 in both jet and in minimum bias events. The results from CDF data from Run 1b have been compared with results from [Formula: see text] passed through the detector simulation program QFL.2