On semi-inclusive rapidity correlations

A model-independent qualitative discussion on semi-inclusive rapidity correlations in high-energy multi-particle production processes is presented. Connection with previous results on the same subject are pointed out. Finally, one discusses semi-inclusive rapidity correlations in terms of reduced rapidities.     

Hidden asymmetry and long range rapidity correlations

Interpretation of long-range rapidity correlations in terms of the fluctuating rapidity density distribution of the system created in high-energy collisions is proposed. When applied to recent data of the STAR Collaboration, it shows a substantial asymmetric component in the shape of this system in central Au–Au collisions, implying that boost invariance is violated on the event-by-event basis even at central rapidity. This effect may seriously influence the hydrodynamic expansion of the system.     

Multiplicity distributions and long range rapidity correlations

The physics of the initial conditions of heavy ion collisions is dominated by the nonlinear gluonic interactions of QCD. These lead to the concepts of parton saturation and the Color Glass Condensate (CGC). We discuss recent progress in calculating multigluon correlations in this framework, prompted by the observation that these correlations are in fact easier to compute in a dense system (nucleus–nucleus) than a dilute one (proton–proton).     

Semiinclusive two-particle correlations and independent cluster emission at ISR energies

Semiinclusive two-particle correlations are calculated in the independent cluster emission model. The resulting semi-inclusive correlation functions ?₂ⁿ(y₁ = y₂ = 0) agree rather than well experimental data, esp. with respect to the multiplicity dependence. The average number of charged particles per cluster found from comparison with semiinclusive data is 2.5 charged particles per cluster, a value found earlier also from analysis of inclusive correlations.     

Inclusive two-and three-particle rapidity correlations in high-energy hadron-nucleus collisions

Three-particle pseudorapidity correlations are investigated for relativistic secondaries from proton-nucleus interactions at 50, 67, 200 and 400 GeV/c and from pion-nucleus interactions at 50 and 200 GeV/c. The experimental data on two- and three-particle correlations are compared with quantitative predictions of current multiple scattering models of nuclear production. Within these models the influence of various factors on the magnitude of correlations is discussed and it is shown, in particular, that energy-momentum conservation plays an essential role at present accelerator energies.     

Two-particle rapidity correlations in proton-nucleus interactions at 300 GeV

The single- and two-particle inclusive rapidity distributions for proton-nucleus interactions at 300 GeV in nuclear emulsions are presented. The analysis of the data with the two-particle rapidity correlation function R(ν₁, ν₂) shows clear evidence of short range correlations. A remarkable asymmetry between projectile and target hemisphere is found.     

Approximation of jet axis in rapidity separated dihadron correlations

The PHENIX experiment has observed particle production asymmetries in transversely polarized proton collisons. This talk presents a novel approach for separating the final-state and initial-state components of the observed asymmetries using the existing PHENIX detector.     

Azimuthal angle and rapidity dependence of di-hadron correlations in QCD

I discuss novel QCD phenomena recently observed in p+p, p+A and A+A collisions, that result from the non-linear dynamics of small-x gluons. I focus on di-hadron correlation measurements, as opposed to single-hadron observables often too inclusive to distinguish possible new effects from established mechanisms. Specifically, I discuss angular correlations of forward di-hadrons in d+Au collisions and long-range rapidity correlations in high-multiplicity p+p and Au+Au collisions.     

Identical particle effect in azimuthal correlations at small rapidity separation

The difference of the short range effect observed in azimuthal correlations of like and unlike particle pairs is interpreted as due to an identical and unidentical boson effect, resp., in the decay of clusters produced in the central region of hadron hadron collisions.     

Analysis of two particle rapidity correlations at ISR energies

The short range two particle rapidity correlations at ISR energies are interpreted in terms of clustering effects in the central rapidity region. It is shown that the experimental data give an indication that large clusters are produced, and as a consequence one should observe short range correlation between π^?′s. The energy dependence of the data is also simply explained.     

Long range rapidity correlations as seen in the STAR experiment

We analyze long range rapidity correlations observed in the STAR experiment at RHIC. Our goal is to extract properties of the two particle correlation matrix, accounting for the analysis method of the STAR experiment. We find a surprisingly large correlation strength for central collisions of gold nuclei at highest RHIC energies. We argue that such correlations cannot be the result of impact parameter fluctuations.     

Inclusive rapidity correlations of π− mesons inpp interactions

Zeitschrift für Physik C Particles and Fields - The simple single-parameter approximation of one-particle semi-inclusive rapidity distributions of negative particles (π? mesons)...     

Fractal behaviour and correlations in rapidity particle distributions at high energies

Recent arguments of Sarcevic and Satz for multifractal behaviour in rapidity particle distributions are shown to have a simple explanation in terms of multisource production in hadron collisions as it happens in the negative binomial approximation. The arguments for strict fractal behaviour may, however, still be justified if use is made of the correlation Mueller moments instead of the factorial moments.     

Inclusive two-particle rapidity correlations at ISR energies and fireball production

ISR data on two-particle rapidity correlations in the region y₁ ≈ y₂ can be understood in terms of the multiperipheral fireball model and indicate an energy independent upper limit of the average fireball mass. The diffractive contribution to the fireball production leads to characteristic shapes of long range correlations. Data on long range rapidity correlations may be used to determine the fractions of non-diffractive and diffractive one- and two-fireball production.     

Effect of Bose-Einstein statistics on two-particle azimuthal and rapidity correlations

The short-range effect in azimuthal and rapidity correlations can be explained within the independent cluster model taking into account the cluster transverse momentum and the Bose-effect (identical particle effect) in the single as well as the two-cluster term. Good agreement with data from Dubna, NAL and ISR is obtained. From the data we determine parameters related to the longitudinal and transverse dimensions of the clusters.     

Many-particle rapidity correlations in light-ion interactions at the CERN intersecting storage rings

Many-particle rapidity correlations have been studied for αα,dd, andpp interactions at the CERN Intersecting Storage Rings using the Split-Field Magnet detector, and basing the investigating on the distributions of rapidity gaps between particles. In the framework of a simple cluster model, it is found that all the data samples have similar features and that the events contain clusters of two different types.     

Two-particle rapidity correlations in 205 GeV/c pp interactions

Using data obtained from an exposure of the 30-inch bubble chamber at NAL, inclusive and semi-inclusive two-particle rapidity correlations are analyzed for charged-charged, ??, ++, and ± particles. For the inclusive sample, positive correlations are observed in the central region. In the semi-inclusive case, the four-and six-prong events exhibit strong positive correlations near 90° CM. Selection of four-prong events with a large rapidity gap shows that the strong correlation seems to be associated with diffractive-type events.