arXiv subjects
Publications and source records attributed to R. S. Longacre.
In this paper we will show that one can summarize the major two particle reaction plane azimuthal correlations for Au + Au mid-central collisions at $\sqrt{s_{NN}} =$ 200 GeV by defining a 2D azimuthal space which is a summary of the event by event average.
In this paper we look into the world data related to the photon and the connection to light mesons with the same spin parity quantum number as the photon $J^p = 1^-$.
In this paper we determine that a local negative correlation(the Hole) in $Δη$ $Δϕ$ space of Au + Au collisions at $\sqrt{s_{NN}}$=200 GeV is caused by strong color QCD electric and magnetic fields which are present in the Glasma Flux Tubes that are generated by the initial conditions.
Squeeze out happen when the expanding central fireball flows around a large surface flux tube in a central Au-Au collision at RHIC. We model such an effect in a flux tube model. Two particle correlations with respect to the $v_2$ axis formed by the soft fireball particles flowing around this large flux tube is a way of measuring the effect.
The Chiral Magnetic Effect (CME) is predicted for Au-Au collisions at RHIC. However many backgrounds can give signals that make the measurement hard to interpret. The STAR experiment has made measurements at different collisions energy ranging from $\sqrt{s_{NN}}$=7.7 GeV to 62.4 GeV. In the analysis that is presented we show that the CME turns on with energy and is not present in central collisions where the induced magnetic is small.
In an earlier paper we developed a Parton Bubble Model (PBM) for RHIC, high-energy heavy-ion collisions. PBM was based on a substructure of a ring of localized bubbles (gluonic hot spots) which initially contain 3-4 partons composed of almost entirely gluons. The bubbles emitted correlated particles at kinetic freezeout, leading to a lumpy fireball surface. For a selection of charged particles (0.8 GeV/c $<$ $p_t$ $<$ 4.0 GeV/c), the PBM reasonably quantitatively (within a few percent) explained high precision RHIC experimental correlation analyses in a manner which was consistent with the small observed HBT source size in this transverse momentum range. We demonstrated that surface emission from a distributed set of surface sources (as in the PBM) was necessary to obtain this consistency. In this paper we give a review of the above comparison to central Au Au collisions. The bubble formation can be associated with gluonic objects predicted by a Glasma Flux Tube Model (GFTM) that formed longitudinal flux tubes in the transverse plane of two colliding sheets of Color Glass Condensate (CGC), which pass through one another. These sheets create boost invariant flux tubes of longitudinal color electric and magnetic fields. A blast wave gives the tubes near the surface transverse flow in the same way it gave transverse flow to the bubbles in the PBM. In the GFTM the longitudinal color electric and magnetic fields have a non-zero topological charge density $F \widetilde F$. These fields cause a local strong CP violation which effects charged particle production coming from quarks and anti-quarks created in the tube or bubble.
In an earlier paper we developed a Parton Bubble Model (PBM) for RHIC/LHC, based on a substructure of a ring of localized bubbles which initially contain 3-4 partons of almost entirely gluons. A Glasma Flux Tube Model (GFTM) which formed longitudinal flux tubes in the transverse plane of two colliding sheets of Color Glass Condensate (CGC) which pass through one another had been developed. These sheets create boost invariant flux tubes of longitudinal color electric and magnetic fields. A blast wave gives the tubes near the surface transverse flow in the same way it gave flow to the bubbles in the PBM. In this paper we connect the equivalent characteristics of the PBM to the GFTM and show that the intermediate transverse momentum charged-two-particle angular correlations of the most central and highest energy RHIC Au + Au collisions are explained. When one considers a 3-4 GeV/c transverse momentum tagged charged trigger particle in combination with other intermediate transverse momentum charged particles, the ridge correlation is generated and explained. The longitudinal color electric and magnetic fields of GFTM have a non-zero topological charge density $F \widetilde $F. These fields cause a local strong CP violation which effects charged particle production coming from quarks and anti-quarks created in the tube or bubble. We developed four-charged-particle correlations which show this CP effect and accumulate from bubble to bubble independent of whether particles are pushed or pulled and rotated in a right or left handed direction, We demonstrate strong evidence for the predicted color electric field using previously published experimental data. We developed 4 particle correlations for obtaining evidence for the predicted color magnetic field.
In an earlier paper we developed a QCD inspired theoretical parton bubble model (PBM) for RHIC/LHC. The PBM quantitatively agreed with the strong charged particle pair correlations observed by the STAR collaboration at RHIC in the highest energy Au + Au central collisions, and also agreed with the Hanbury Brown and Twiss (HBT) observed small final state source size approximately 2f radii in the transverse momentum range above 0.8 GeV/c. The model assumed a substructure of a ring of localized adjoining 2f radius bubbles(gluonic hot spots) perpendicular to the collider beam direction, centered on the beam, at mid-rapidity and located on the expanding fireball surface of the Au + Au collisions. In this paper we extend the model (PBME) to include the changing development of bubbles with centrality from the most central region where bubbles are very important to the most peripheral where the bubbles are gone. Energy density is found to be related to bubble formation and as centrality decreases the maximum energy density and bubbles shift from symmetry around the beam axis to the reaction plane region causing a strong correlation of bubble formation with elliptic flow. We obtained reasonably quantitative agreement (within a few percent of the total correlations) with a new precision RHIC experiment which extended the centrality region investigated to the range 0-80% (most central to most peripheral). The characteristics and behavior of the bubbles imply they represent a significant substructure formed on the surface of the fireball at kinetic freezeout
We show the preliminary charged-particle pair correlation analyses presented in a poster session at the 2006 International Quark Matter Conference in Shanghai China. The correlation analysis space of $Δϕ$ (azimuth) and $Δη$ (pseudo-rapidity) are considered as a function of centrality for minimum bias Au + Au collisions in the mid-transverse momentum range in the STAR detector. The analyses involve unlike-sign charge pairs and like-sign charge pairs, which are transformed into charge-dependent (CD) signals and charge-independent (CI) signals. We use a multiplicity scale to compare the different centralities. We find the signals increase with increasing centrality. A model featuring dense gluonic hot spots as first proposed by van Hove predicts that the observables under investigation would have sensitivity to such a substructure should it occur. A blast wave model including multiple hot spots motivates the selection of transverse momenta in the range 0.8 GeV/c$ < p_t < $4.0 GeV/c.
A $ρ(770)^0$ mass shift of about -40 MeV/$c^2$ was measured in $p+p$ collisions at $\sqrt{s_{_{NN}}} = $ 200 GeV at RHIC. Previous mass shifts have been observed at CERN-LEBC-EHS and CERN-LEP. We will show that phase space does not account for the $ρ(770)^0$ mass shift measured at RHIC, CERN-LEBC-EHS and CERN-LEP and conclude that there are significant scattering interactions in $p+p$ collisions.
Four separate experiments, observing the OZI forbidden disconnected reaction pi- p -> phi phi n with increasing statistics were consistent. These experiments very selectively completely broke down the OZI suppression by 3 phi phi resonances with IG JPC = 0+ 2++ in the observed mass region 2.038 to 2.600 GeV. The only viable proposed explanation has been that the IG JPC = 0+ 2++ Glueball expected in this mass region caused the hard glue in the disconnection to resonate and very selectively breakdown the OZI suppression for its quantum numbers only. Recently a p p central production spin analysis found the f2(1950) had a dominant decay mode f2(1270) pi pi. We consider if it is related to the phi phi resonances, and find that it likely is.
Since the early eighties, we have shared with Leon Van Hove the following view. That if a QGP were produced in high energy heavy ion colliders, that its hadronization products would likely come from small localized in phase space bubbles of plasma. We develop a model based on HIJING, to which we added a ring of adjoining multiple bubbles in the central rapidity region. Our simulations were designed to be tested by the forthcoming RHIC STAR detector data for 65 GeV/n Au colliding with 65 GeV/n Au. We took into account background and resonance effects to allow a direct comparison with the data. Later 100 GeV/n Au colliding with 100 GeV/n Au and LHC data could also test these ideas. We used two charged particle correlation's as a sensitive method to test for bubbles.
Two cylindrical forward TPC detectors are described which were constructed to extend the phase space coverage of the STAR experiment to the region 2.5 < |η| < 4.0. For optimal use of the available space and in order to cope with the high track density of central Au+Au collisions at RHIC, a novel design was developed using radial drift in a low diffusion gas. From prototype measurements a 2-track resolution of 1-2 mm is expected.
We discuss the problem of observing spontaneous parity and CP violation in collision systems. We discuss and propose observables which may be used in heavy-ion collisions to observe such violations, as well as event-by-event methods to analyze the data. Finally, we discuss simple monte-carlo models of these CP violating effects which we have used to develop our techniques and from which we derive rough estimates of sensitivities to signals which may be seen at RHIC.
The recent papers of Jeon and Koch [1] and Asakawa, Heinz, and Muller [2] argue that the event by event fluctuations of the ratio of the positively charged and negatively charged pions provide a distinct signal for a QGP at RHIC/LHC due to differences in those from the QGP phase and the Hadron Gas Phase.In this paper we point out that aside from the questionability of the many assumptions in the treatment used,even following their approach there are other effects not considered, e.g. color charge fluctuations, which could significantly or even completely wash out the proposed signal.Therefore lack of observation of these charge fluctuation signals cannot lead one to conclude that a QGP is not formed at RHIC. A general discussion of experimental requirements for observation of such signals(if they exist),annd how to interpret them is included.
A fast, simple to use Monte Carlo based event generator is presented which is intended to facilitate simulation studies and the development of analysis software for the Solenoidal Tracker at RHIC (Relativistic Heavy Ion Collider) (STAR) experiment at the Brookhaven National Laboratory (BNL). This new event generator provides a fast, convenient means for producing large numbers of uncorrelated A+A collision events which can be used for a variety of applications in STAR, including quality assurance evaluation of event reconstruction software, determination of detector acceptances and tracking efficiencies, physics analysis of event-by-event global variables, studies of strange, rare and exotic particle reconstruction, and so on. The user may select the number of events, the particle types, the multiplicities, the one-body momentum space distributions and the detector acceptance ranges. The various algorithms used in the code and its capabilities are explained. Additional user information is also discussed. The computer code implementation is called MEVSIM.
The baryon-baryon continuum invariant mass spectrum generated from relativistic nucleus + nucleus collision data may reveal the existence of doubly-strange dibaryons not stable against strong decay if they lie within a few MeV of threshold. Furthermore, since the dominant component of these states is a superposition of two color-octet clusters which can be produced intermediately in a color-deconfined quark-gluon plasma (QGP), an enhanced production of dibaryon resonances could be a signal of QGP formation. A total of eight, doubly-strange dibaryon states are considered for experimental search using the STAR detector (Solenoidal Tracker at RHIC) at the new Relativistic Heavy Ion Collider (RHIC). These states may decay to Lambda-Lambda and/or proton-Cascade-minus, depending on the resonance energy. STAR's large acceptance, precision tracking and vertex reconstruction capabilities, and large data volume capacity, make it an ideal instrument to use for such a search. Detector performance and analysis sensitivity are studied as a function of resonance production rate and width for one particular dibaryon which can directly strong decay to proton-Cascade-minus but not Lambda-Lambda. Results indicate that such resonances may be discovered using STAR if the resonance production rates are comparable to coalescence model predictions for dibaryon bound states.
We believe that one can have serious reservations as to whether heavy ion collisions (e.g. 100 GeV/n Au + 100 GeV/n Au) can lead to Thermal and Chemical equilibrium over large regions (particularly if it is assumed this happens whenever QGP is produced at RHIC-that is if it is produced). It is at present not clear that the collision dynamics and times available will lead to this. An alternate scenario proposed by Van Hove where localized in rapidity bubbles of plasma may well be more probable, and may well occur at least some of the time, and some of the time mainly survive to the final state. If this occurs we have developed a series of event generators to extend and describe these phenomena. A Van Hove type[6,7] spherical bubble at eta=0 is embedded in a resonable event generator in qualitative agreement with Hijing etc[12]. The plasma bubble hadronized at a temperature of 170 Mev according to the model developed by Koch, Muller and Rafelski[21]. The amount of available bubble energy is selected by that in a small central circular cross-section of radius approx 1.3fm or 2.5fm in 100 Gev/n Au+AU, central events The results predict Possible Striking Signals for a QGP. We are also applying these techniques to investigating Kharzeev and Pisarski bubbles of metastable vacua with odd CP.