Heavy Flavor Physics

To minimize multiple scattering and photon conversion after n o decay, which also creates non-primary vertex tracks, detector material will be kept to a minimum throughout the tracking system. @ The co_ffiguration of the STAR experiment is shown in Fig. 1.1. Momentum measurements will be made at midrapidity over a large pseudo-rapidity range (Irl I < 2) with f_all azimuthal coverage (A(])= 2n). Particle identification will be performed within Itil < 1. The detection system will consist of a time projection chamber (TPC) and a silicon vertex tracker (SVT) inside a solenoidal magnet to enable tracking, @ momentum analysis, particle identification via dE/dx and location of primary and secondary vertices. Detectors will be installed to provide a collision geometry trigger. These include a central trigger scintillator barrel around the TPC, vertex position detectors near the bearnline just outside the magnet, and calorimeters located in the region oi: the beam insertion magnets to selectively veto events according to the number @ of spectators. An electromagnetic calorimeter, for which outside funding is being sought, wiU be located outside the magnet and used to trigger on transverse energy and measure jet cross sections. The major physics goals of STAR. can be accomplished with this cor_!iguration of detectors. A time-of-flight system surrounding the TPC for particle identification at higher momenta and external time projection chambers outside the @ magnet to extend the rl coverage are anticipated as upgrades. A summary of the detector systems is presented in 'Fable 1-1. 1.C. Cost and Schedule The STAR detector system will contain the TPC, SVT, EMC, TOF, external TPC, @ solenoid magnet, electronics, data acquisition, and trigger as major systems..The cost of the detector has been developed in four iterations, over a 6-month period, each subject to review. The estimates made in FY92 dollars include materials, labor, EDIA and contingency, and are based on a variety of inputs including vendor quotes, estimates from comparable systems, and engineering estimates. The TPC, solenoid magnet, @ electronics, data acquisition, trigger system, controls, on-line computing, detector : conventional systems, detector testing, detector installation, systems integration and project management will be funded primarily by the RHIC construction project. Funding for the TOF, EMC, and external TPC systems will be sought from other sources. The SVT_which is especially important to the initial physics program_will @ be supported through the prototype phase by RHIC R&D funds and constructed thereafter using other resources.

The decay rates of QQ mesons (Q ε c, b) are studied in the NRQCD formalism in terms of their short distance and long distance coefficients. The long distance coefficients are obtained through phenomenological potential model description of the mesons. The mass spectrum of the cc and bb mesons are reviewed in non-relativistic phenomenological quark antiquark potential of the type V (r) = − α c r + Ar ν , with ν varying from 0.5 to 2. The spin hyperfine and spin-orbit interactions are employed to obtain the masses of the pseudoscalar and vector mesons. The digamma and dileptonic decays of cc, and bb mesons are investigated using some of the known potential models by incorporating radiative corrections up to the lowest order. The heavy quarkonium decays into two photons, and the vector state into lepton pairs are computed within the NRQCD formalism. Our theoretical predictions of the decays of the cc and bb mesons and the results obtained from some of the other potential schemes are compared with the experimental values.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We report the investigation of the first order flow of charmed quarks in gold-to-gold collision at the energy near to the speed of the light using A Multi-Phase Transport (AMPT) model. We have used the AMPT string melting version known as partonic interactions option. In this study, we investigated the directed flow v1 of the charmed quark D0 as a function of rapidity. The model predicts the correct sign for D0v1, but the size of the predicted directed flow signal is too small by about an order of magnitude comparing to the real data from the STAR collaboration analysis. The AMPT model shows that the charm quark v1 magnitude is larger than that of the light quarks at large rapidity. This indicates that the charm quarks can retain more information from initial condition than the light quarks.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

 Conservation of heavy Flavor always produced in pair  Large mass produced in early phase when temperature is high  Small number isolated from bulk system serves as probe to QGP  Large momentum transfer required for production pQCD can safely be applied  Medium effect different models to explain experimental data pQCD based models? Experiment shows!!!!! Some spectacular experimental results on heavy quarks at both RHIC and LHC The results shows similar heavy quark suppression to that of gluons and lighter mesons. How to describe these results? sQGP or pQCD ?

This article focuses on interpreting theories when they are functioning in an ongoing investigation. The sustained search for a quark-gluon plasma serves as a prime example. The analysis treats the Standard Model of Particle Physics as an Effective Field Theory. Related effective theories functioning in different energy ranges can have different functional ontologies, or models of the reality treated. A functional ontology supplies a categorial framework that grounds and limits the language used in describing experiments and reporting results. The scope and limitations of such a local functional realism are evaluated.

We report updates to an ongoing lattice-QCD calculation of the form factors for the semileptonic decays B → π ν, B s → K ν, B → π + − , and B → K + −. The tree-level decays B (s) → π(K) ν enable precise determinations of the CKM matrix element |V ub |, while the flavor-changing neutral-current interactions B → π(K) + − are sensitive to contributions from new physics. This work uses MILC's (2+1+1)-flavor HISQ ensembles at approximate lattice spacings between 0.057 and 0.15 fm, with physical sea-quark masses on four out of the seven ensembles. The valence sector is comprised of a clover b quark (in the Fermilab interpretation) and HISQ light and s quarks. We present preliminary results for the form factors f 0 , f + , and f T , including studies of systematic errors.

The field of ultrarelativistic heavy ion collisions is today a flourishing activity both on the experimental and on the theoretical side. Although the theoretical justifications to study these collisions was given already more than three decades ago and the experimental studies have a history of more than 25 years we are still very much in the dark as to the details of the processes and of the characteristics of the matter created in collisions. Increasing the energy of collisions has brought new insights but has also resulted with new challenges. In the present paper I will try from a personal perspective to report on the answers we have collected and on the problems we are faced with. The account is partial, taking into account that it is impossible to render justice to every aspect of the field.

The exact QCD is one of the cornerstones of particle physics. Hence it would appear that there should exist no physical situation where a broken version of QCD may have any relevance. However, here I shall show that a spontaneously broken version of QCD may have been significant in an early universe scenario. How this can be made compatible with the exact QCD shall be pointed out. This gives rise to a new cosmological dark matter object (called &quot;rungion&quot;).

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We present a study of the heavy-light spectrum and of the D-and B-meson decay constants. The results were obtained in the quenched approximation, by using the nonperturbatively improved Clover lattice action at β = 6.2, with a sample of 100 configurations, on a 24 3 × 64 lattice. After a careful analysis of the systematic errors present in the extraction of the physical results, by assuming quite conservative discretization errors, we find f Ds = 231 ± 12

Charm production in deep inelastic ep scattering was measured with the ZEUS detector using an integrated luminosity of 354 pb−1. Charm quarks were identified by reconstructing D ± mesons in the D ± → K ∓π±π± decay channel. Lifetime information was used to reduce combinatorial background substantially. Differential cross sections were measured in the kinematic region 5 &lt; Q 2 &lt; 1000 GeV2, 0.02 &lt; y &lt; 0.7, 1.5 &lt; p T (D ±) &lt; 15 GeV and |η(D ±)| &lt; 1.6, where Q 2 is the photon virtuality, y is the inelasticity, and p T (D ±) and η(D ±) are the transverse momentum and the pseudorapidity of the D ± meson, respectively. Next-to-leading-order QCD predictions are compared to the data. The charm contribution, $ F_2^{{c\overline{c}}} $ , to the proton structure-function F 2 was extracted.

We have studied the behaviour of the nuclear modification factor as a function of centrality, chemical baryon potential and thermal freeze out temperature using the data coming from the Fast Hadron Freezeout Generator. Considering two ways of NMF definition, namely the ratio of meson yields and ratio of baryons yield, we considered two associates effects (for percolation cluster formation) to identify it; appearance of the anomalous nuclear transparency and light nuclei production. In this paper we have used the behaviour of nuclear modification factor as a function of different physical parameters to get the information of the behavior of nuclear transparency effect and the nuclear coalescence in freezeout state. We have chosen different generators for this purpose. Here we have used the simulated data for Au-Au collisions at RHIC energies coming from the FASTMC Model. This model is very good in freezeout state.

 Conservation of heavy Flavor always produced in pair  Large mass produced in early phase when temperature is high  Small number isolated from bulk system serves as probe to QGP  Large momentum transfer required for production pQCD can safely be applied  Medium effect different models to explain experimental data pQCD based models? Experiment shows!!!!! Some spectacular experimental results on heavy quarks at both RHIC and LHC The results shows similar heavy quark suppression to that of gluons and lighter mesons. How to describe these results? sQGP or pQCD ?

We give a progress report on a project aimed at a high-precision calculation of the decay constants f B and f B s from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light sea-quark mass ratios m ud /m s , including approximately physical sea-quark masses. This range of parameters provides excellent control of the continuum limit and of heavy-quark discretization errors. We present a preliminary error budget with projected uncertainties of 2.2 MeV and 1.5 MeV for f B and f B s , respectively.

We report on the status of our calculation of the hadronic matrix elements for neutral B-meson mixing with asqtad sea and valence light quarks and using the Wilson clover action with the Fermilab interpretation for the b quark. We calculate the matrix elements of all five local operators that contribute to neutral B-meson mixing both in and beyond the Standard Model. We use MILC ensembles with N f = 2 + 1 dynamical flavors at four different lattice spacings in the range a ≈ 0.045-0.12 fm, and with light sea-quark masses as low as 0.05 times the physical strange quark mass. We perform a combined chiral-continuum extrapolation including the so-called wrongspin contributions in simultaneous fits to the matrix elements of the five operators. We present a complete systematic error budget and conclude with an outlook for obtaining final results from this analysis.

We give a progress report on a project aimed at a high-precision calculation of the decay constants f B and f B s from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light sea-quark mass ratios m ud /m s , including approximately physical sea-quark masses. This range of parameters provides excellent control of the continuum limit and of heavy-quark discretization errors. We present a preliminary error budget with projected uncertainties of 2.2 MeV and 1.5 MeV for f B and f B s , respectively. Figure 1: Left: heavy valence-quark masses and ensemble lattice spacings in this study for different light to strange sea-quark-mass ratios m l /m s. The symbol radius is proportional to the data sample size. The red line indicates the cut am h = 0.9; the blue, am h = 0.5. Faint symbols indicate omitted data. Right: Spectrum ...

We report on the status of our calculation of the hadronic matrix elements for neutral $B$-meson mixing with asqtad sea and valence light quarks and using the Wilson clover action with the Fermilab interpretation for the $b$ quark. We calculate the matrix elements of all five local operators that contribute to neutral $B$-meson mixing both in and beyond the Standard Model. We use MILC ensembles with $N_f=2+1$ dynamical flavors at four different lattice spacings in the range $a \approx 0.045$--$0.12$~fm, and with light sea-quark masses as low as 0.05 times the physical strange quark mass. We perform a combined chiral-continuum extrapolation including the so-called wrong-spin contributions in simultaneous fits to the matrix elements of the five operators. We present a complete systematic error budget and conclude with an outlook for obtaining final results from this analysis.

The Solenoidal Tracker at RHIC (STAR) experiment utilizes its excellent mid-rapidity tracking and particle identification capabilities to study the emergent properties of Quantum Chromodynamics (QCD). The STAR heavy-ion program at vanishingly small baryon density is aimed to address questions about the quantitative properties of the stronglyinteracting Quark Gluon Plasma (QGP) matter created in high energy collisions (η/s,q, chirality, transport parameters, heavy quark diffusion coefficients ...). At finite baryon density, the questions concern the phases of nuclear matter (the QCD phase diagram) and the nature of the phase transition, namely: what is the onset collision energy for the formation of QGP? What is the nature of phase transition in heavy-ion collisions? Are there two phase transition regions? If yes, where is the critical point situated? At Quark Matter 2015, the STAR collaboration has presented a wealth of new experimental results which address these questions. In these proceedings I highlight a few of those results.

During the RHIC 2010 run, STAR has collected a large amount of minimum-bias, central and high p T trigger data in Au+Au collisions at √ s NN = 39, 62.4 and 200 GeV with the detector configured to minimize photon conversion background. In this article we report on a new high precision measurement of non-photonic electron mid-rapidity invariant yield, improved nuclear modification factor and v 2 in Au+Au collisions at √ s NN = 200 GeV. We also present measurements of mid-rapidity invariant yield at √ s NN = 62.4 and v 2 at √ s NN = 39 and 62.4 GeV.

During the RHIC 2010 run, STAR has collected a large amount of minimum-bias, central and high p T trigger data in Au+Au collisions at √ s NN = 39, 62.4 and 200 GeV with the detector configured to minimize photon conversion background. In this article we report on a new high precision measurement of non-photonic electron mid-rapidity invariant yield, improved nuclear modification factor and v 2 in Au+Au collisions at √ s NN = 200 GeV. We also present measurements of mid-rapidity invariant yield at √ s NN = 62.4 and v 2 at √ s NN = 39 and 62.4 GeV.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

Recently we have conjectured that (in-)elastic collisions of (pre-)hadronic high momentum states with the bulk of hadrons in the late fireball might substantially account for the attenuation of the high transverse momentum hadrons at RHIC. The potential hadronic attenuation has therefore to be addressed in further detail before definite conclusions on possible QCD effects in a deconfined QGP phase can be drawn with respect to the materializing jets. From our transport studies we find that the interactions of fully formed hadrons are practically negligible in central Au+Au collisions at √ s = 200 GeV for p ⊥ ≥ 6 GeV/c, but have some importance for the shape of the ratio R AA at lower p ⊥ (≤ 6 GeV/c). However, a significant part of the large suppression seen experimentally is attributed to inelastic interactions of 'leading' jet-like prehadrons with the dense hadronic environment. In addition, we also show within this scenario first (preliminary) results of nearside and far-side correlations of high p ⊥ particles from central Au+Au collisions at √ s = 200 GeV. It turns out that the nearside correlations are unaltered-in accordance with experimentwhereas the far-side correlations are suppressed by ∼ 60%. Since the experimental observation is a nearly complete disappearance of the far-side jet there should be some additional and earlier partonic interactions in the dense and possibly colored medium.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.

This article focuses on interpreting theories when they are functioning in an ongoing investigation. The sustained search for a quark-gluon plasma serves as a prime example. The analysis treats the Standard Model of Particle Physics as an Effective Field Theory. Related effective theories functioning in different energy ranges can have different functional ontologies, or models of the reality treated. A functional ontology supplies a categorial framework that grounds and limits the language used in describing experiments and reporting results. The scope and limitations of such a local functional realism are evaluated.

We present our methods to fit the two point correlators for light, strange, and charmed pseudoscalar meson physics with the highly improved staggered quark (HISQ) action. We make use of the least-squares fit including the full covariance matrix of the correlators and including Gaussian constraints on some parameters. We fit the correlators on a variety of the HISQ ensembles. The lattice spacing ranges from 0.15 fm down to 0.06 fm. The light sea quark mass ranges from 0.2 times the strange quark mass down to the physical light quark mass. The HISQ ensembles also include lattices with different volumes and with unphysical values of the strange quark mass. We use the results from this work to obtain our preliminary results of f D , f D s , f D s / f D , and ratios of quark masses presented in another talk [1].

The Fermilab Lattice and MILC Collaborations Lattice calculations of the form factors for the charm semileptonic decays D → Klν and D → πlν provide inputs to direct determinations of the CKM matrix elements |V cs | and |V cd | and can be designed to validate calculations of the form factors for the bottom semileptonic decays B → πlν and B → Kll. We are using Fermilab charm (bottom) quarks and asqtad staggered light quarks on the 2+1 flavor asqtad MILC ensembles to calculate the charm (bottom) form factors. We outline improvements to the previous calculation of the charm form factors and detail our progress. We expect our current round of data production to allow us to reduce the theoretical uncertainties in |V cs | and |V cd | from 10.5% and 11%, respectively, to about 7%.

We give a progress report on a project aimed at a high-precision calculation of the decay constants f B and f B s from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light sea-quark mass ratios m ud /m s , including approximately physical sea-quark masses. This range of parameters provides excellent control of the continuum limit and of heavy-quark discretization errors. We present a preliminary error budget with projected uncertainties of 2.2 MeV and 1.5 MeV for f B and f B s , respectively.

We report on the status of our calculation of the hadronic matrix elements for neutral B-meson mixing with asqtad sea and valence light quarks and using the Wilson clover action with the Fermilab interpretation for the b quark. We calculate the matrix elements of all five local operators that contribute to neutral B-meson mixing both in and beyond the Standard Model. We use MILC ensembles with N f = 2 + 1 dynamical flavors at four different lattice spacings in the range a ≈ 0.045-0.12 fm, and with light sea-quark masses as low as 0.05 times the physical strange quark mass. We perform a combined chiral-continuum extrapolation including the so-called wrongspin contributions in simultaneous fits to the matrix elements of the five operators. We present a complete systematic error budget and conclude with an outlook for obtaining final results from this analysis.

We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC.