CDFII Detector Research Articles

Axion dark matter and additional BSM aspects in an extended 2HDM setup

We illustrate and discuss the phenomenology of a model featuring a two-Higgs doublet sector augmented by two SU(2) singlet scalars. The gauge symmetry group is extended as well with a U(1)Lμ−Lτ component whose spontaneous breaking leads to the gauge boson which has an important effect in the muon (g−2). A global PQ symmetry is introduced upon its breaking; we have the axion particle which is also dark matter (DM) in our work. In particular, we have focused on type-X and type-II 2HDM models and found out that (g−2) cannot be explained only by the scalar sector for type-II 2HDM mainly due to stringent constraint from b→sγ resulted in MH±>800 GeV. For type-II 2HDM, we can have axion coupling with the gluons which generates the axion potential and possible explanation for the strong CP problem. The proposed model accommodates neutrino masses via the type-I seesaw mechanism with an upper bound on the right-handed neutrino mass 1 GeV (1 TeV) for type-II (type-X) 2HDM due to the presence of Planck scale suppressed operators. Moreover, we also have additional scalars which affect the oblique parameters and hence the W-boson mass which leads us to explain the W-boson mass observed at the CDF-II detector. The most stringent constraints on the masses and quartic couplings come from the perturbativity and potential bound from the below conditions which leads to fine-tuning among the parameters in part of the parameter space. Finally, we discuss the possible detection prospects of the axion DM and the additional gauge boson. Published by the American Physical Society 2024

Measurement of the top-quark mass in the all-hadronic channel using the full CDF data set

The top-quark mass M_top is measured using top quark-antiquark pairs produced in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV and decaying into a fully hadronic final state. The full data set collected with the CDFII detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.3 fb-1, is used. Events are selected that have six to eight jets, at least one of which is identified as having originated from a b quark. In addition, a multivariate algorithm, containing multiple kinematic variables as inputs, is used to discriminate signal events from background events due to QCD multijet production. Templates for the reconstructed top-quark mass are combined in a likelihood fit to measure M_top with a simultaneous calibration of the jet-energy scale. A value of M_top = 175.07+- 1.19(stat)+1.55-1.58(syst) GeV/c^2 is obtained for the top-quark mass.

Probabilistic particle flow algorithm for high occupancy environment

Algorithms based on the particle flow approach are becoming increasingly utilized in collider experiments due to their superior jet energy and missing energy resolution compared to the traditional calorimeter-based measurements. Such methods have been shown to work well in environments with low occupancy of particles per unit of calorimeter granularity. However, at higher instantaneous luminosity or in detectors with coarse calorimeter segmentation, the overlaps of calorimeter energy deposits from charged and neutral particles significantly complicate particle energy reconstruction, reducing the overall energy resolution of the method. We present a technique designed to resolve overlapping energy depositions of spatially close particles using a statistically consistent probabilistic procedure. The technique is nearly free of ad-hoc corrections, improves energy resolution, and provides new important handles that can improve the sensitivity of physics analyses: the uncertainty of the jet energy on an event-by-event basis and the estimate of the probability of a given particle hypothesis for a given detector response. When applied to the reconstruction of hadronic jets produced in the decays of tau leptons using the CDF-II detector at Fermilab, the method has demonstrated reliable and robust performance.

Search for a Low-Mass Standard Model Higgs Boson in theττDecay Channel inpp¯Collisions ats=1.96 TeV

We report on a search for the standard model Higgs boson decaying into pairs of τ leptons in pp collisions produced by the Tevatron at sqrt[s]=1.96 TeV. The analyzed data sample was recorded by the CDFII detector and corresponds to an integrated luminosity of 6.0 fb(-1). The search is performed in the final state with one τ decaying leptonically and the second one identified through its semihadronic decay. Since no significant excess is observed, a 95% credibility level upper limit on the production cross section times branching ratio to the ττ final state is set for hypothetical Higgs boson masses between 100 and 150 GeV/c2. For a Higgs boson of 120 GeV/c2 the observed (expected) limit is 14.6 (15.3) the predicted value.

Observation ofBs0→J/ψK*(892)0andBs0→J/ψKS0decays

We report the first observation of two Cabibbo-suppressed decay modes of the B0_s meson. Using a sample of p-pbar collisions at sqrt{s}=1.96 TeV corresponding to 5.9 fb-1 of integrated luminosity collected with the CDFII detector at the Fermilab Tevatron, we search for new B0_s decay modes in a sample of events containing J/psi to mu+ mu- decays. We reconstruct a B0_s to J/psi K*(892)0 signal with K^*(892)0 to K+ pi-, observing a yield of 151 +/- 25 events with a statistical significance of 8.0 sigma. We also reconstruct a B0_s to J/psi K0_S signal with K0_S to pi+ pi-, observing a yield of 64 +/- 14 events with a statistical significance of 7.2 sigma. From these yields, we extract the branching ratios B(B0_s -> J/psi K*(892)0)= (8.3 +/- 3.8) x 10{-5} and B(B0_s -> J/psi K0)= (3.5 +/- 0.8) x 10{-5}, where statistical, systematic and fragmentation fraction uncertainties are included in the combined uncertainty.

DiffractiveWandZproduction at the Fermilab Tevatron

We report on a measurement of the fraction of events with a W or Z boson which are produced diffractively in antiproton-proton collisions at a center of mass energy of 1.96 TeV, using data from 0.6 inverse femtobarns of integrated luminosity collected with the CDF-II detector equipped with a Roman-pot spectrometer that detects the antiproton (pbar) from pbar+p --> pbar+[X+W/Z]. We find that (1.00+/- 0.11)% of Ws and (0.88+/-0.22)% of Zs are produced diffractively in a region of antiproton or proton fractional momentum loss (\xi) of 0.03<\xi<0.10 and 4-momentum transferred squared t of -1<t<0 (GeV/c)^2, where we account for the events in which the proton scatters diffractively while the antiproton dissociates, pbar+p --> [X+W/Z]+p, by doubling the measured proton dissociation fraction. We also report on searches for W and Z production in double Pomeron exchange, p+pbar --> p+[X+W/Z]+pbar, and on exclusive Z production, pbar+p --> pbar+Z+p. No signal is seen above background for these processes, and comparisons are made with expectations.

Measurement of the top quark mass andpp¯→tt¯cross section in the all-hadronic mode with the CDF II detector

We present a measurement of the top quark mass and of the top-antitop pair production cross section using p-pbar data collected with the CDFII detector at the Tevatron Collider at the Fermi National Accelerator Laboratory and corresponding to an integrated luminosity of 2.9 fb-1. We select events with six or more jets satisfying a number of kinematical requirements imposed by means of a neural network algorithm. At least one of these jets must originate from a b quark, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the absolute jet energy scale (JES) is measured simultaneously with the top quark mass. The measurement yields a value of 174.8 +- 2.4(stat+JES) ^{+1.2}_{-1.0}(syst) GeV/c^2, where the uncertainty from the absolute jet energy scale is evaluated together with the statistical uncertainty. The procedure measures also the amount of signal from which we derive a cross section, sigma_{ttbar} = 7.2 +- 0.5(stat) +- 1.0 (syst) +- 0.4 (lum) pb, for the measured values of top quark mass and JES.

Measurement of thepp¯→tt¯production cross section and the top quark mass ats=1.96 TeVin the all-hadronic decay mode

We report the measurements of the t anti-t production cross section and of the top quark mass using 1.02 fb^-1 of p anti-p data collected with the CDFII detector at the Fermilab Tevatron. We select events with six or more jets on which a number of kinematical requirements are imposed by means of a neural network algorithm. At least one of these jets must be identified as initiated by a b-quark candidate by the reconstruction of a secondary vertex. The cross section is measured to be sigma_{tt}=8.3+-1.0(stat.)+2.0-1.5(syst.)+-0.5(lumi.) pb, which is consistent with the standard model prediction. The top quark mass of 174.0+-2.2(stat.)+-4.8(syst.) GeV/c^2 is derived from a likelihood fit incorporating reconstructed mass distributions representative of signal and background.

Measurement of thett¯production cross section inpp¯collisions ats=1.96 TeVin the all hadronic decay mode

We report a measurement of the ttbar production cross section using the CDF-II detector at the Fermilab Tevatron. The analysis is performed using 311 pb-1 of ppbar collisions at sqrt(s)=1.96 TeV. The data consist of events selected with six or more hadronic jets with additional kinematic requirements. At least one of these jets must be identified as a b-quark jet by the reconstruction of a secondary vertex. The cross section is measured to be sigma(tbart)=7.5+-2.1(stat.)+3.3-2.2(syst.)+0.5-0.4(lumi.) pb, which is consistent with the standard model prediction.

Searches for new physics in photon final states

The Run I results on the searches for new physics in photon final states were intriguing. The rare eeγγ≠ET candidate event and the measured event rate for the signature ℓ+γ+≠ET, which was 2.7 sigma above the Standard Model predictions, sparked signature-based searches in the γγ+X and ℓγ+X channels. With more data in Run II we should be able to answer a simple question: was it an anomaly or were the Run I results the first evidence for new physics? We present searches for new physics in photon final states at CDF Run II, Fermilab, with substantially more data and a higher p̄p collision energy, 1.96 TeV, and the upgraded CDF-II detector.

A 96-channel FPGA-based Time-to-Digital Converter (TDC) and fast trigger processor module with multi-hit capability and pipeline

We describe an field-programmable gate arrays based (FPGA), 96-channel, Time-to-Digital converter (TDC) and trigger logic board intended for use with the Central Outer Tracker (COT) [T. Affolder et al., Nucl. Instr. and Meth. A 526 (2004) 249] in the CDF Experiment [The CDF-II detector is described in the CDF Technical Design Report (TDR), FERMILAB-Pub-96/390-E. The TDC described here is intended as a further upgrade beyond that described in the TDR] at the Fermilab Tevatron. The COT system is digitized and read out by 315 TDC cards, each serving 96 wires of the chamber. The TDC is physically configured as a 9U VME card. The functionality is almost entirely programmed in firmware in two Altera Stratix FPGAs. The special capabilities of this device are the availability of 840 MHz LVDS inputs, multiple phase-locked clock modules, and abundant memory. The TDC system operates with an input resolution of 1.2 ns, a minimum input pulse width of 4.8 ns and a minimum separation of 4.8 ns between pulses. Each input can accept up to 7 hits per collision. The time-to-digital conversion is done by first sampling each of the 96 inputs in 1.2-ns bins and filling a circular memory; the memory addresses of logical transitions (edges) in the input data are then translated into the time of arrival and width of the COT pulses. Memory pipelines with a depth of 5.5 μ s allow deadtime-less operation in the first-level trigger; the data are multiple-buffered to diminish deadtime in the second-level trigger. The complete process of edge-detection and filling of buffers for readout takes 12 μ s . The TDC VME interface allows a 64-bit Chain Block Transfer of multiple boards in a crate with transfer-rates up to 47 Mbytes/s. The TDC module also produces prompt trigger data every Tevatron crossing via a deadtimeless fast logic path that can be easily reprogrammed. The trigger bits are clocked onto the P3 VME backplane connector with a 22-ns clock for transmission to the trigger. The full TDC design and multi-card test results are described. There is no measurable cross-talk between channels; linearity is limited by the least-count time bin. The physical simplicity ensures low-maintenance; the functionality being in firmware allows reprogramming for other applications.

Experience with parallel optical link for the CDF silicon detector

The Dense Optical Interface Module is a byte-wide optical link developed for the Run II upgrade of the CDF silicon tracking system (CDF Collaboration, The CDF-II Detector Technical Design Report, FERMILAB-Pub 96/390-E; S. Nahn, status of CDF silicon, Vertex 2002, Nucl. Instr. and Meth.). The module consists of a transmitter with a laser-diode array for conversion of digitized detector signals into light outputs, a 22 m optical fiber ribbon cable for light transmission, and a receiver converting the light pulses back to electrical signals. We report on the design feature, characteristics, and radiation tolerance.

The CDFII Time-of-Flight detector and impact on beauty flavor tagging

The new CDFII detector incorporates a Time-of-Flight detector (TOF), employing plastic scintillator bars and fine-mesh photomultipliers. Since August 2001 the TOF system has been fully instrumented and integrated into the CDFII data acquisition system. With a design goal of 100 ps resolution the TOF system will provide at least two standard deviations separation between K ± and π ± for momenta p < 1.6 GeV/ c, complementing low momentum particle identification by means of the specific ionization energy loss measured in the drift chamber. We describe the design of the TOF detector and discuss the current status of its calibration and initial performances. Finally we review the expected impact of the TOF detector in the flavor tagging of neutral B s 0 meson.

Identification of cosmic rays using drift chamber hit timing

The CDFII detector at Fermilab contains a large drift chamber called the Central Outer Tracker (COT) which is used for measuring the trajectories of charged particles. We describe a method of identifying COT tracks as cosmic rays by using the drift chamber as a distributed time-of-flight detector.