Collider Detector At Fermilab Research Articles

Scidac-Data: Enabling Data Driven Modeling of Exascale Computing

The SciDAC-Data project is a DOE-funded initiative to analyze and exploit two decades of information and analytics that have been collected by the Fermilab data center on the organization, movement, and consumption of high energy physics (HEP) data. The project analyzes the analysis patterns and data organization that have been used by NOvA, MicroBooNE, MINERvA, CDF, D0, and other experiments to develop realistic models of HEP analysis workflows and data processing. The SciDAC-Data project aims to provide both realistic input vectors and corresponding output data that can be used to optimize and validate simulations of HEP analysis. These simulations are designed to address questions of data handling, cache optimization, and workflow structures that are the prerequisites for modern HEP analysis chains to be mapped and optimized to run on the next generation of leadership-class exascale computing facilities.We present the use of a subset of the SciDAC-Data distributions, acquired from analysis of approximately 71,000 HEP workflows run on the Fermilab data center and corresponding to over 9 million individual analysis jobs, as the input to detailed queuing simulations that model the expected data consumption and caching behaviors of the work running in high performance computing (HPC) and high throughput computing (HTC) environments. In particular we describe how the Sequential Access via Metadata (SAM) data-handling system in combination with the dCache/Enstore-based data archive facilities has been used to develop radically different models for analyzing the HEP data. We also show how the simulations may be used to assess the impact of design choices in archive facilities.

KMR kt-factorization procedure for the description of the LHCb forward hadron–hadron Z0 production at [formula omitted

Quite recently, two sets of new experimental data from the LHCb and the CMS Collaborations have been published, concerning the production of the Z0 vector boson in hadron–hadron collisions with the center-of-mass energy ECM=s=13TeV. On the other hand, in our recent work, we have conducted a set of semi-NLO calculations for the production of the electro-weak gauge vector bosons, utilizing the unintegrated parton distribution functions (UPDF) in the frameworks of Kimber–Martin–Ryskin (KMR) or Martin–Ryskin–Watt (MRW) and the kt-factorization formalism, concluding that the results of the KMR scheme are arguably better in describing the existing experimental data, coming from D0, CDF, CMS and ATLAS Collaborations. In the present work, we intend to follow the same semi-NLO formalism and calculate the rate of the production of the Z0 vector boson, utilizing the UPDF of KMR within the dynamics of the recent data. It will be shown that our results are in good agreement with the new measurements of the LHCb and the CMS Collaborations.

Analyses of whole transverse momentum distributions in pp̄ and pp collisions by using a modified version of Hagedorn’s formula

To describe the transverse momentum [Formula: see text] distribution of charged hadrons at 1.96 TeV observed by the CDF collaboration, we propose a formula with two components, namely, hadron gas distributions and inverse power laws inspired by QCD calculus. The new formula based on a formula by Hagedorn in 1983 includes an integration of pseudo-rapidity [Formula: see text]. The data collected at 0.9, 2.76, 7 and 13 TeV by the ALICE, CMS, and ATLAS collaborations are also analyzed using various models including single component models as well as two-component models. The results by the use of the modified version of Hagedorn’s formula are compared with those by the use of the two-component model proposed by Bylinkin, Rostovtsev and Ryskin (BRR). We investigate whether or not there is an interrelation among our modified formula, a formula proposed by ATLAS collaboration, and the BRR formula. Moreover, formulas for the [Formula: see text] distributions in the nonextensive approach are discussed.

Data preservation at the Fermilab Tevatron

The Fermilab Tevatron collider's data-taking run ended in September 2011, yielding a dataset with rich scientific potential. The CDF and D0 experiments each have approximately 9PB of collider and simulated data stored on tape. A large computing infrastructure consisting of tape storage, disk cache, and distributed grid computing for physics analysis with the Tevatron data is present at Fermilab. The Fermilab Run II data preservation project intends to keep this analysis capability sustained through the year 2020 and beyond. To achieve this goal, we have implemented a system that utilizes virtualization, automated validation, and migration to new standards in both software and data storage technology and leverages resources available from currently-running experiments at Fermilab. These efforts have also provided useful lessons in ensuring long-term data access for numerous experiments, and enable high-quality scientific output for years to come.

Measurement of low-pTD+-meson production cross-section at CDF II

In this paper I report on a measurement of the low-pTD+-meson production cross-section in proton-antiproton collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the CDF experiment at the Tevatron collider during Run II. The measurement is performed in a yet unexplored low transverse momentum range, down to 1.5 GeV/c. The actual QCD theory cannot predict the behavior of the strong interactions in the low transferred-four-momentum region because in these kinematic conditions the strong coupling constant is of the order of the unity. Thus, a perturbative expansion is not useful. At present, several phenomenological models have been proposed, but they are able to describe only a few aspects of the observed physical quantities and not the full complexity. Experimental results in these conditions are then crucial to test new QCD models. The measurement of the differential cross section at low pT plays an important role in this context allowing refinement of current knowledge. While these results lie within the band of theoretical uncertainty, differences in shape suggest that theoretical predictions can benefit from further refinement taking account of them.

X,YandZStates

Many new states in the charmonium mass region were recently discovered by BaBar, Belle, CLEO-c, CDF, D0, BESIII, LHCb and CMS Collaborations. We use the QCD Sum Rule approach to study the possible structure of some of these states.

Strong decays of D_{3}^{*}(2760), D_{s3}^{*}(2860), B_{3}^{*}, and B_{s3}^{*}

In this paper, we study the OZI-allowed two-body strong decays of 3^- heavy–light mesons. Experimentally the charmed D_{3}^{*}(2760) and the charm–strange D_{s3}^{*}(2860) states with these quantum numbers have been discovered. For the bottomed B(5970) state, which was found by the CDF Collaboration recently, its quantum number has not been decided yet and we assume it is a 3^- meson in this paper. The theoretical prediction for the strong decays of bottom–strange state B_{s3}^* is also given. The relativistic wave functions of 3^- heavy mesons are constructed and their numerical values are obtained by solving the corresponding Bethe–Salpeter equation with instantaneous approximation. The transition matrix is calculated by using the PCAC and low energy theorem, following which the decay widths are obtained. For D_{3}^*(2760) and D_{s3}^*(2860), the total strong decay widths are 72.6 and 47.6 MeV, respectively. For B_3^* with M=5978 MeV and B_{s3}^* with M=6178 MeV, their strong decay widths are 22.9 and 40.8 MeV, respectively.

Physics Results from the Thirty Years of the CDF Experiment

Physics Results from the Thirty Years of the CDF Experiment

Determination of the muonic branching ratio of the W boson and its total width via cross-section measurements at the Tevatron and LHC

The total $W$-boson decay width $\Gamma_W$ is an important observable which allows testing of the standard model. The current world average value is based on direct measurements of final state kinematic properties of $W$-boson decays, and has a relative uncertainty of 2%. The indirect determination of $\Gamma_W$ via the cross-section measurements of vector-boson production can lead to a similar accuracy. The same methodology leads also to a determination of the leptonic branching ratio. This approach has been successfully pursued by the CDF and D0 experiments at the Tevatron collider, as well as by the CMS collaboration at the LHC. In this paper we present for the first time a combination of the available measurements at hadron colliders, accounting for the correlations of the associated systematic uncertainties. Our combination leads to values of $\textrm{BR}(W\rightarrow\mu\nu)=(10.72 \pm 0.16)\%$ and $\Gamma_W = 2113 \pm 31$ MeV, respectively, both compatible with the current world averages.

Excited bottom and bottom-strange mesons in the quark model

In order to understand the possible $q\bar{q}$ quark-model assignments of the $B_J(5840)$ and $B_J(5960)$ recently reported by the LHCb Collaboration, we evaluate mass spectra, strong decays, and radiative decays of bottom and bottom-strange mesons in a nonrelativistic quark model. Comparing these predictions with the relevant experimental results, we suggest that the $B_J(5840)$ and $B_J(5960)$ can be identified as the $B(2^1S_0)$ and $B(1^3D_3)$, respectively, and the $B(5970)$ reported by the CDF Collaboration can be interpreted as the $B(2^3S_1)$ or $B(1^3D_3)$. Further precise measurements of the width, spin and decay modes of the $B(5970)$ are needed to distinguish these two assignments. These predictions of bottom and bottom-strange mesons can provide useful information to further experimental investigations.

Measurement ofsin2θeffleptusinge+e−pairs fromγ*/Zbosons produced inpp¯collisions at a center-of-momentum energy of 1.96 TeV

At the Fermilab Tevatron proton-antiproton ($p\bar{p}$) collider, Drell-Yan lepton pairs are produced in the process $p \bar{p} \rightarrow e^+e^- + X$ through an intermediate $\gamma^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribution of the $e^-$ as a function of the $e^+e^-$-pair mass is used to obtain $\sin^2\theta^{\rm lept}_{\rm eff}$, the effective leptonic determination of the electroweak-mixing parameter $\sin^2\theta_W$. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.4~fb$^{-1}$ of integrated luminosity from $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $\sin^2\theta^{\rm lept}_{\rm eff}$ is found to be $0.23248 \pm 0.00053$. The combination with the previous CDF measurement based on $\mu^+\mu^-$ pairs yields $\sin^2\theta^{\rm lept}_{\rm eff} = 0.23221 \pm 0.00046$. This result, when interpreted within the specified context of the standard model assuming $\sin^2 \theta_W = 1 - M_W^2/M_Z^2$ and that the $W$- and $Z$-boson masses are on-shell, yields $\sin^2\theta_W = 0.22400 \pm 0.00045$, or equivalently a $W$-boson mass of $80.328 \pm 0.024 \;{\rm GeV}/c^2$.

Measurement of the forward–backward asymmetry of top-quark and antiquark pairs using the full CDF Run II data set

We measure the forward--backward asymmetry of the production of top quark and antiquark pairs in proton-antiproton collisions at center-of-mass energy $\sqrt{s} = 1.96~\mathrm{TeV}$ using the full data set collected by the Collider Detector at Fermilab (CDF) in Tevatron Run II corresponding to an integrated luminosity of $9.1~\rm{fb}^{-1}$. The asymmetry is characterized by the rapidity difference between top quarks and antiquarks ($\Delta y$), and measured in the final state with two charged leptons (electrons and muons). The inclusive asymmetry, corrected to the entire phase space at parton level, is measured to be $A_{\text{FB}}^{t\bar{t}} = 0.12 \pm 0.13$, consistent with the expectations from the standard-model (SM) and previous CDF results in the final state with a single charged lepton. The combination of the CDF measurements of the inclusive $A_{\text{FB}}^{t\bar{t}}$ in both final states yields $A_{\text{FB}}^{t\bar{t}}=0.160\pm0.045$, which is consistent with the SM predictions. We also measure the differential asymmetry as a function of $\Delta y$. A linear fit to $A_{\text{FB}}^{t\bar{t}}(|\Delta y|)$, assuming zero asymmetry at $\Delta y=0$, yields a slope of $\alpha=0.14\pm0.15$, consistent with the SM prediction and the previous CDF determination in the final state with a single charged lepton. The combined slope of $A_{\text{FB}}^{t\bar{t}}(|\Delta y|)$ in the two final states is $\alpha=0.227\pm0.057$, which is $2.0\sigma$ larger than the SM prediction.

Measurements of the top quark mass with the D0 detector

The mass of the top quark is a fundamental parameter of the standard model (SM) and has to be determined experimentally. In this talk, I present the most recent measurements of the top quark mass in pp‾ collisions at s=1.96 TeV recorded by the D0 experiment at the Fermilab Tevatron Collider. The measurements are performed in final states containing two leptons, using 5.4 fb-1 of integrated luminosity, and one lepton, using 9.7 fb-1 of integrated luminosity. The latter constitutes the most precise single measurement of the mass of the top quark, corresponding to a relative precision of 0.43%. I conclude with a combination of our results with the results by the CDF collaboration, attaining a relative precision of 0.37%.

Vector boson + heavy flavor production at the Tevatron

Studies of the associated production of heavy-flavor bottom and charm quarks with vector bosons (W, Z, and γ) provide important tests of perturbative quantum chromodynamics calculations. These studies also improve constraints on parton distribution functions, and improve our understanding of major backgrounds in Higgs studies and searches for new phenomena. In these proceedings, we present several measurements of vector boson plus heavy-flavor quark production at Tevatron experiments CDF and D0, including measurements of cross-sections for Z+c/b jets, γ+b jet, ϒ+W/Z, and W/Z+D⁎ production processes. These results include the first measurements of Z+c production at the Tevatron, as well as the lowest-momentum measurements of charmed meson production in association with W and Z bosons at the Tevatron.

B-meson production at Tevatron and the LHC in the Regge limit of quantum chromodynamics

We study the inclusive hadroproduction of B0, B+, and Bs0 mesons in the leading order in the parton Reggeization approach. We have described B-meson transverse momentumdistributionsmeasured in the central region of rapidity by the CDF Collaboration at Fermilab Tevatron and CMS Collaboration at LHC within uncertainties and without free parameters, applying Kimber–Martin–Ryskin unintegrated gluon distribution function in a proton.

Event generator tunes obtained from underlying event and multiparton scattering measurements

New sets of parameters (“tunes”) for the underlying-event (UE) modelling of the pythia8, pythia6 and herwig++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE proton–proton (mathrm {p}mathrm {p}) data at sqrt{s} = 7,text {TeV} and to UE proton–antiproton (mathrm {p}overline{mathrm{p}} ) data from the CDF experiment at lower sqrt{s}, are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton–proton collisions at 13,text {TeV}. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to “minimum bias” (MB) events, multijet, and Drell–Yan ( mathrm{q} overline{mathrm{q}} rightarrow mathrm{Z}/ gamma ^* rightarrow lepton-antilepton+jets) observables at 7 and 8,text {TeV}, as well as predictions for MB and UE observables at 13,text {TeV}.

Measurement of the single top quark production cross section and|Vtb|in 1.96 TeVpp¯collisions with missing transverse energy and jets and final CDF combination

An updated measurement of the single top quark production cross section is presented using the full data set collected by the Collider Detector at Fermilab (CDF) and corresponding to 9.5 fb${}^{-1}$ of integrated luminosity from proton-antiproton collisions at 1.96 TeV center-of-mass energy. The events selected contain an imbalance in the total transverse energy, jets identified as originating from $b$ quarks, and no identified leptons. The sum of the $s$- and $t$-channel single top quark cross sections is measured to be $3.53_{-1.16}^{+1.25}$ pb and a lower limit on $V_{tb}$ of 0.63 is obtained at the 95% credibility level. These measurements are combined with previously reported CDF results obtained from events with an imbalance in total transverse energy, jets identified as originating from $b$ quarks, and exactly one identified lepton. The combined cross section is measured to be $3.02_{-0.48}^{+0.49}$ pb and a lower limit on $V{tb}$ of 0.84 is obtained at the 95% credibility level.

Data preservation at the Fermilab Tevatron

The Fermilab Tevatron collider's data-taking run ended in September 2011, yielding a dataset with rich scientific potential. The CDF and DO experiments each have nearly 9 PB of collider and simulated data stored on tape. A large computing infrastructure consisting of tape storage, disk cache, and distributed grid computing for physics analysis with the Tevatron data is present at Fermilab. The Fermilab Run II data preservation project intends to keep this analysis capability sustained through the year 2020 or beyond. To achieve this, we are implementing a system that utilizes virtualization, automated validation, and migration to new standards in both software and data storage technology as well as leveraging resources available from currently-running experiments at Fermilab. These efforts will provide useful lessons in ensuring long-term data access for numerous experiments throughout high-energy physics, and provide a roadmap for high-quality scientific output for years to come.

Heavy flavor at the Tevatron

The CDF and D0 experiments at the Tevatron proton-antiproton collider have pioneered and established the role of hadron collisions in exploring flavor physics through a broad program that continues to offer competitive results. I report on latest results in the flavor sector obtained using the whole CDF and D0 data sets corresponding to ∼ 10 fb−1 of integrated luminosity; including B-mesons spectroscopy and production asymmetries, flavor specific decay bottom-strange mesons lifetime. I also present measurements of direct and indirect CP violation in bottom and charm meson decays.

Fragmentation fractions of two-body b-baryon decays

We study the fragmentation fractions (fBb) of the b-quark to b-baryons (Bb). By the assumption of fΛb/(fu+fd)=0.25±0.15 in accordance with the measurements by LEP, CDF and LHCb Collaborations, we estimate that fΛb=0.175±0.106 and fΞb−,0=0.019±0.013. From these fragmentation fractions, we derive B(Λb→J/ψΛ)=(3.3±2.1)×10−4, B(Ξb−→J/ψΞ−)=(5.3±3.9)×10−4 and B(Ωb−→J/ψΩ−)>1.9×10−5. The predictions of B(Λb→J/ψΛ) and B(Ξb−→J/ψΞ−) clearly enable us to test the theoretical models, such as the QCD factorization approach in the b-baryon decays.