Creating small circular, elliptical, and triangular droplets of quark-gluon plasma

The experimental study of the collisions of heavy nuclei at relativistic energies has established the properties of the quark-gluon plasma (QGP), a state of hot, dense nuclear matter in which quarks and gluons are not bound into hadrons. In this state, matter behaves as a nearly inviscid fluid that efficiently translates initial spatial anisotropies into correlated momentum anisotropies among the produced particles, producing a common velocity field pattern known as collective flow. In recent years, comparable momentum anisotropies have been measured in small-system proton-proton ($p$$+$$p$) and proton-nucleus ($p$$+$$A$) collisions, despite expectations that the volume and lifetime of the medium produced would be too small to form a QGP. Here, we report on the observation of elliptic and triangular flow patterns of charged particles produced in proton-gold ($p$$+$Au), deuteron-gold ($d$$+$Au), and helium-gold ($^3$He$+$Au) collisions at a nucleon-nucleon center-of-mass energy $\sqrt{s_{_{NN}}}$~=~200 GeV. The unique combination of three distinct initial geometries and two flow patterns provides unprecedented model discrimination. Hydrodynamical models, which include the formation of a short-lived QGP droplet, provide a simultaneous description of these measurements.

The experimental study of the collisions of heavy nuclei at relativistic energies has established the properties of the quark-gluon plasma (QGP), a state of hot, dense nuclear matter in which quarks and gluons are not bound into hadrons [1][2][3][4].In this state, matter behaves as a nearly inviscid fluid [5] that efficiently translates initial spatial anisotropies into correlated momentum anisotropies among the produced particles, creating a common velocity field pattern known as collective flow.In recent years, comparable momentum anisotropies have been measured in small-system proton-proton (p+p) and proton-nucleus (p+A) collisions, despite expectations that the volume and lifetime of the medium produced would be too small to form a QGP.Here, we report on the observation of elliptic and triangular flow patterns of charged particles produced in proton-gold (p+Au), deuterongold (d+Au), and helium-gold ( 3 He+Au) collisions at a nucleon-nucleon center-of-mass energy √ s N N = 200 GeV.The unique combination of three distinct initial geometries and two flow patterns provides unprecedented model discrimination.Hydrodynamical models, which include the formation of a short-lived QGP droplet, provide a simultaneous description of these measurements.
Experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) explore emergent phenomena in quantum chromodynamics, most notably the near-perfect fluidity of the QGP.To quantify this behavior, the azimuthal distribution of each event's final-state particles, dN  dφ , is decomposed into a Fourier series as follows: where p T and φ are the transverse momentum and the azimuthal angle of a particle relative to the beam direction, respectively, and ψ n is the orientation of the n th order symmetry plane of the produced particles.The second (v 2 ) and third (v 3 ) Fourier coefficients represent the amplitude of elliptic and triangular flow, respectively.A multitude of measurements of the Fourier coefficients, utilizing a variety of techniques, have been well-described by hydrodynamical models, thereby establishing the fluid nature of the QGP in large-ion collisions [5].
The LHC experiments were first to observe similar features in small-system collisions [6][7][8][9], followed closely by reanalysis of previously recorded d+Au data from RHIC [10,11].These unexpected results highlighted the need to explore whether these smallest hadronic systems still form QGP. Alternatively, a number of physics mechanisms that do not involve QGP formation have been proposed, including those which attribute final-state momentum anisotropy to momentum correlations generated at the earliest stages of the collision, hence referred to as initial-state momentum correlation models (see Refs. [12] and [13] for recent reviews).
A projectile geometry scan utilizing the unique capabilities of RHIC was proposed in Ref. [14] in order to discriminate between hydrodynamical models that couple to the initial geometry and initial-state momentum correlation models that do not.Varying the collision system from p+Au, to d+Au, to 3 He+Au changes the initial geometry from dominantly circular, to elliptical, and to triangular configurations, respectively, as characterized by the 2 nd and 3 rd order spatial eccentricities, which correspond to ellipticity and triangularity, respectively.The n th order spatial eccentricity of the system, ε n , typically determined from a Monte Carlo (MC) Glauber model of nucleon-nucleon interactions (see e.g.Ref [15]), can be defined as where r and φ are the polar coordinates of participating nucleons [16].The eccentricity fluctuates event-by-event and is generally dependent on the impact parameter of the collision and the number of participating nucleons.The mean ε 2 and ε 3 values for small impact parameter p/d/ 3 He+Au collisions are shown in Fig. 1a.The ε 2 and ε 3 values in d+Au and 3 He+Au are driven almost entirely by the intrinsic geometry of the deuteron and 3 He, while the values in p+Au collisions are driven by fluctuations in the configuration of struck nucleons in the Au nucleus, as the proton itself is on average circular.Hydrodynamical models begin with an initial spatial energy-density distribution with a given temperature that evolves in time following the laws of relativistic viscous hydrodynamics using an equation of state determined from lattice QCD [17].Examples of this evolution are shown for p/d/ 3 He+Au collisions in Fig. 1b using the hydrodynamical model sonic [18].The first panel of each row shows the temperature profile at time t = 1.0 fm/c for typical p+Au, d+Au, and 3 He+Au collisions.The following three panels show snapshots of the temperature evolution at three different time points.The initial spatial distribution also sets the pressure gradient field, which translates into a velocity field, which in turn determines the azimuthal momentum distribution of produced particles.The relative magnitude and direction of the velocity is represented in the figure by arrows.At the final time point, t = 4.5 fm/c, the mostly circular (top), elliptical (middle), and triangular (bottom) initial spatial eccentricities have been translated into dominantly radial, elliptic, and triangular flow, respectively.Given these different initial geometries, as characterized by the ε 2 and ε 3 values shown in Fig. 1a, hydrodynamical models provide a clear prediction for the ordering of the experimentally accessible v 2 and v 3 signals, following that of the ε n , namely x This ordering assumes that hydrodynamics can efficiently translate the initial geometric ε n into dynamical v n , which in turn requires a small value for the specific shear viscosity.
There exist a class of alternative explanations where v n is not generated via flow, but rather is created at the earliest time in the collision process as described by socalled initial-state momentum correlation models.They produce a mimic flow signal where the initial collision generates color flux tubes that have a preference to emit particles back-to-back in azimuth [19,20].These color flux tubes, also referred to as domains, have a transverse size relative to the collision axis less than the colorcorrelation length of order 0.1-0.2fm.In the case where individual domains are resolved, a collision system with a larger overall area but the same characteristic domain size (for example d+Au and 3 He+Au compared with p+Au and p+p) should have a weaker correlation because the different domains are separated and do not communicate [21,22].An instructive analogy is a ferromagnet with many domains: if the domains are separated and disconnected, the overall magnetic field is weakened by the cancellation of effects from the random orientation in the different domains.The RMS diameter of the deuteron is 4.2 fm, and so in d+Au collisions the two hot spots are much further apart than the characteristic domain size.A straightforward prediction is then that the v 2 and v 3 coefficients should be ordered in contradistinction to the hydrodynamic flow prediction.An experimental realization of the proposed geometry scan has been under way since 2014 at RHIC.Collisions of 3 He+Au, p+Au, and d+Au at GeV were recorded in 2014, 2015, and 2016, respectively.The PHENIX experiment observed elliptic anisotropies in the azimuthal distributions of the charged particles produced in all three systems [23][24][25], as well as triangular anisotropies in 3 He+Au collisions [25].This Letter completes this set of elliptic and triangular flow measurements from PHENIX in all three systems and explores the relation between the strength of the measured v n and the initial-state geometry.The v n measurements reported here are determined using the event plane method [26] for charged hadrons in the midrapidity region covering |η| < 0.35, where η is the particle pseudorapidity, and θ is the polar angle of the particle.The 2 nd order event plane is determined using detectors in the Augoing direction covering −3.0 < η < −1.0 in p/d+Au and −3.9 < η < −3.1 in 3 He+Au.The 3 rd order event plane is determined using detectors in the Au-going direction covering −3.9 < η < −3.1 in all cases.The pseudorapidity gap between the particle measurements and the event plane determination excludes auto-correlations and reduces short-range correlations arising from, for example, jets and particle decays-typically referred to as nonflow correlations.Estimates of possible remaining nonflow contributions are included in the systematic uncertainties.Additional uncertainties related to detector alignment, data selection, and event plane determination are also included in the systematic uncertainty estimation.
In these small collision systems the event plane resolution is low, meaning that v n {EP} = v 2 n [27] and the results are therefore equivalent to measurements using two-particle correlation methods.
Measurements of v n as a function of p T are shown for all three systems in Fig. 2. The measurements are performed in the 0-5% most central events, an experimentally determined criterion which selects the 5% of events with the largest number of produced particles (hereafter referred to simply as "multiplicity") in the region −3.9 < η < −3.1.A detailed description of the centrality determination in small systems is given in Ref. [28].The vertical bars on each point represent the statistical uncertainties, while the shaded boxes represent the systematic uncertainties.The flow coefficients follow the prediction of hydrodynamical models shown in equation (3).These relationships suggest that the primary driver of azimuthal momentum anisotropies in particle emission is initial spatial anisotropy.
While Fig. 2 offers qualitative support for the hydrodynamic theory, Fig. 3 directly compares these data to predictions from two hydrodynamical models, sonic [18] (used in Fig. 1) and iEBE-VISHNU [29].The core structure of the two models is similar: the initial conditions are evolved using viscous hydrodynamics, the fluid hadronizes, hadronic scattering occurs, and the v n coefficients of the final-state hadron distributions are determined using two-particle correlation methods.However, the detailed implementations are different, including the use of different fluctuations in the initial energy deposited, as well as different hadronic rescattering packages.Both calculations in Fig. 3 use a ratio of the shear viscosity η to entropy density s of η/s = 0.08 ≈ 1 4π , the conjectured lower limit in strongly-coupled field theories [30].
Figure 3 shows that the hydrodynamical models are consistent with the v 2 data in all three systems.Both models capture the magnitude difference of v 3 compared to v 2 , the collision system dependence, as well as the general p T dependence of v 3 .The models tend to diverge at higher p T in the case of v 3 , which may be more sensitive to the hadronic rescattering.To quantify the agreement, we calculate p-values following the procedure of incorporating data systematic uncertainties and their correlations into a modified χ 2 analysis laid out in Ref. [31] (See Methods for details).We find that sonic and iEBE-VISHNU yield combined p-values across the 6 measurements of 0.96 and 0.061 respectively.The large difference in p-values is driven by the effect of the dominant nonflow uncertainty, which is asymmetric and anti-correlated between v 2 and v 3 .sonic tends to underestimate the v 2 and overestimate the v 3 , particularly in p+Au and d+Au, which is more in line with the uncertainty correlations than iEBE-VISHNU, which tends to yield a poorer description of the p T slope.Overall, the simultaneous description of these two observables in three different systems using a common initial geometry model and the same specific η/s strongly supports the hydrodynamic picture.
The hydrodynamic calculations shown in Fig. 3 use initial conditions generated from a nucleon Glauber model.However, initial geometries with quark substructure do not significantly change the ε 2 and ε 3 values for high multiplicity p/d/ 3 He+Au collisions [32,33] and thus the hydrodynamic results should be relatively insensitive to these variations.
While we have focused on hydrodynamical models here, there is an alternative class of models that also translate initial spatial eccentricity to final state particle azimuthal momentum anisotropy.Instead of hydrodynamic evolution, the translation occurs via partonparton scattering with a modest interaction cross section.These parton transport models, for example A Multi-Phase Transport (ampt) Model [34], are able to capture the system ordering of v n at low-p T in small systems [35], but fail to describe the p T dependence and overall magnitude of the coefficients for all systems resulting in a p-value consistent with zero when compared to the data shown here.We have additionally analyzed ampt following the identical PHENIX event plane method and find even worse agreement with the experimental data.
While the initial geometry models for the d+Au and 3 He+Au are largely constrained by our detailed understanding of the 2-and 3-body nucleon correlations in the deuteron and 3 He nuclei, respectively, the distribution of deposited energy around each nucleon-nucleon collision site could result in an ambiguity between the allowed ranges of the η/s and the broadening of the initial distribution, as pointed out in Ref. [13].However, a broader distribution of deposited energy results in a significant reduction of the ε 2 values and an even greater reduction of ε 3 , with by far the largest reduction in the p+Au system.Here again, the simultaneous constraints of the elliptic and triangular flow ordering eliminates this ambiguity.
Our experimental data also rule out the initial-state correlations scenario where color domains are individually resolved as the dominant mechanics for creating v 2 and v 3 in p/d/ 3 He+Au collisions.After our results became publicly available, a new calculation was presented in Ref. [37], hereafter referred to as MSTV, where the ordering of the measured v n values matches the experimental data.This calculation posits that gluons from the Au target do not resolve individual color domains in the projectile p/d/ 3 He and interact with them coherently, and thus the ordering does not follow Eq. 4. The calculations are shown in Fig. 3, and yield a p-value for the MSTV calculations of v 2 and v 3 for the three collision systems of effectively zero, in contradistinction to the robust values found for the hydrodynamic models.Another key statement made by MSTV -that in the dilute-dense limit the saturation scale Q 2 s is proportional to the number of produced charged particles -is questionable [38], but also leads the MSTV authors to make a clear prediction that the v 2 will be identical between systems when selecting on the same event multiplicity.Shown in Fig. 4 are the previously published d+Au (20-40%) and p+Au (0-5%) v 2 where the measured mean charged particle multiplicities (dN ch /dη) match [36].The results do not support the MSTV prediction of an identical v 2 for these two systems at the same multiplicity, while the differences in v 2  [36].Blue and red curves correspond to sonic predictions for d+Au and p+Au, respectively.The green curve corresponds to MSTV calculations for 0-5% central p+Au collisions, which the authors state are also applicable to d+Au collisions at the same multiplicity.
between the systems follow the expectations from hydrodynamic calculations matched to the same dN ch /dη.
In summary, we have shown azimuthal particle correlations in three different small-system collisions with different intrinsic initial geometries.The simultaneous constraints of v 2 and v 3 in p/d/ 3 He+Au collisions definitively demonstrate that the v n 's are correlated to the initial geometry, removing any ambiguity related to event multiplicity or initial geometry models.We find that initial-state momentum correlation models where color domains are individually resolved are ruled out as the dominant mechanism behind the observed collectivity.New calculations where the domains are not resolved are unable to simultaneously explain the v 2 and v 3 in high multiplicity collisions, and are further unable to explain the difference in v 2 between p+Au and d+Au when the multiplicity selections are matched.Further, we find that hydrodynamical models which include QGP formation provide a simultaneous and quantitative description of the data in all three systems.tor (FVTX) covering 1.0 < |η| < 3.0 and composed of high efficiency silicon mini-strips [40] provides an independent event plane angle determination.A description of the PHENIX detector can be found in Ref. [41].
Event Selection: A minimum bias (MB) interaction trigger is provided by the BBC, which requires at least one hit tube in both the south (η < 0, Au-going direction) and north (η > 0, p/d-going direction), along with an online vertex within |z vertex | < 10 cm of the nominal interaction region.In addition to the MB trigger, a high multiplicity trigger requiring > 35 (> 40) hit tubes in the BBCS provided a factor of 25 (188) enhancement of high multiplicity events in p+Au (d+Au) collisions.A more precise offline collision vertex is determined using timing information in the BBC and is constrained to |z vertex | < 10 cm in order to be sufficiently inside the acceptance of the detector.Events containing more than one nucleus-nucleus collision, referred to as double interaction events, are rejected using an algorithm based on BBC charge and timing information described in Ref. [24].Event centrality is determined using the total charge collected in the south BBC, as described in Ref. [28].We require an event centrality of 0-5% to select events with the highest multiplicity, where the signal of interest is strongest.In total, 322 (636) million p+Au (d+Au) events are analyzed.
Track Selection: Quality cuts are applied to reconstructed particle tracks requiring hits in both the DC and the outermost PC layer with a required 3σ level of agreement.This removes the majority of tracks that do not originate from the primary collision.Further details can be found in Refs.[23][24][25].
Event Plane Determination: The third-order symmetry plane angle, ψ 3 is measured using the south BBC via the standard method [42].Namely, where N is the number of particles and φ i is the azimuthal angle of each particle.The ψ 3 resolution, R(ψ 3 ), is calculated using the three-subevent method which correlates measurements in the south BBC, south FVTX, and central arms.The calculated resolutions are 6.7% and 5.7% in p+Au and d+Au collisions, respectively.Determination of v 3 : The v 3 values are measured using the event plane method [26,42] as where φ is the azimuthal angle of particles emitted at midrapitiy, |η| < 0.35.

Systematic uncertainties:
The systematic uncertainties reported are estimated according to the following methods for the measurements of v 3 in both p+Au and d+Au collisions.
The effect of remaining background tracks due primarily to photon conversions and weak decays is estimated by comparing the v 3 values when requiring a tighter matching between the track projection and hits in PC3.We find that this increases the v 3 by < 1% and 7% in p+Au and d+Au collisions, respectively, independent of p T .
The effect of double interaction event selection is estimated by comparing the v 3 values when requiring a tighter cut on the rejection.This yields a change in the v 3 of 3% and 2% in p+Au and d+Au collisions respectively, independent of p T .
Uncertainty in the event plane resolution comes from two sources.The first is the statistical uncertainty inherent in the resolution calculation, which yields a ±13% and ±17% uncertainty in p+Au and d+Au collisions, respectively.Additionally, the resolution is calculated using central arm tracks over two different p T regions.This leads to an uncertainty of 7% and 34% in p+Au and d+Au collisions, respectively.
We also include an uncertainty due to the choice of event plane detector.In p+Au collisions, this is determined by comparing the v 3 calculated using event planes determined by the south BBC and FVTX.We find that the results are consistent within uncertainties, as expected.In d+Au collisions, v 3 is also calculated using an alternative method utilizing two particle correlations.Based on a ratio of the v 3 values calculated using the two particle correlation and event plane methods, we assign a 16% systematic uncertainty.
In v 3 , nonflow decreases the amplitude of the measured signal [25], and its contribution increases with increasing p T .To estimate the nonflow contribution we calculate a normalized correlation function between midrapidity tracks and BBC photomultiplier (PMT) tubes: where Q PMT is the charge on the PMT in the pair and N track(p T )−PMT same event is the number of track-PMT pairs from the same event.M (∆φ, p T ) is determined in the same way as S(∆φ, p T ) but with one particle in one event and another particle in a different event (the so-called mixed event technique).This normalization procedure accounts for acceptance effects and produces a correlation function of order unity.Next, we fit C(∆φ, p T ) with a Fourier expansion: We do this process for both systems in which we want to estimate the nonflow (p+Au or d+Au) and for p+p at the same collision energy.We take the Fourier coefficients c n to find the nonflow contribution to the v n values in a given system, where Q is the average BBC charge for the system.The ratio of average charges normalizes the c n by multiplicity.
The assumption is that c p+p n is entirely due to nonflow such that the deviation of the nonflow ratio from one is taken as an estimate of the nonflow, and included as a p T dependent systematic uncertainty.
A summary of the systematic uncertainties on v 3 in p/d+Au are given in Table I along with 3 He+Au uncertainties taken from Ref. [25].
Comparison of theory to data: The level of agreement between the different theoretical calculations and the data presented in this work is quantified by performing a least squares fit incorporating a careful treatment of various types of systematic uncertainties, following Ref.[31].
The nonflow uncertainty is the dominant source of systematic uncertainty in all six measurements.It is known to be point-to-point correlated as a function of p T , to contribute asymmetrically, and to be anti-correlated between v 2 and v 3 .Namely, the nonflow can only reduce the measured v 2 while simultaneously only increasing the v 3 .
All remaining measurement uncertainties are assumed to be uncorrelated between v 2 and v 3 .The remaining uncertainties are assumed to contribute in the following ways: 1. as point-to-point uncorrelated uncertainties 2. as point-to-point anti-correlated uncertainties (e.g. a tilt in the p T dependence)

as point-to-point correlated uncertainties
The total systematic uncertainty (excluding the nonflow) is taken to contribute a fraction of its value to each of the above types.A conservative approach is taken, and these fractions are allowed to vary independently for each measurement within reasonable limits.The bands around the theoretical calculations shown in Fig. 3 indicate some subset of theoretical uncertainties which differs between the models.We make the assumption that the dominant contribution is a point-to-point correlated uncertainty which is additionally correlated between v 2 and v 3 .Given their small uncertainties, the inclusion of this treatment has little effect on the results for either sonic or MSTV.It has the largest effect with iEBE-VISHNU, however its inclusion does not affect the relative ordering of the agreement discussed below.
We calculate a p-value from the least squares minimization in the standard way, where the number of degrees of freedom is simply the total number of data points, as there are no free parameters in the comparison.The total p-values, along with the p-values for each collision system, are given in Table II for sonic, iEBE-VISHNU, MSTV, and ampt.The ampt calculations are taken from Ref. [35], which calculate v 2 and v 3 relative to the initial participant nucleon plane, utilizing the so-called string melting mechanism, and a parton interaction cross section of σ = 1.5 mb.sonic provides a very good description of the data, with a rather close to unity value of 0.96, which may indicate a modest overestimate of the statistical or systematic uncertainties.iEBE-VISHNU yields a worse p-value of 0.061.The larger p-value for sonic compared to iEBE-VISHNU is driven by the nonflow uncertainty.The fact that sonic tends to underpredict the v 2 while over-predicting the v 3 is mitigated by the nonflow uncertainty, while iEBE-VISHNU's worse description of the p T dependence in p+Au and d+Au is not compensated for by the relatively small remaining uncertainty Both MSTV and ampt yield a very poor description of the data with p-values of 8.83 × 10 −17 and 1.71 × 10 −46 respectively.

FIG. 1 .
FIG. 1. | Average system eccentricities from a Monte Carlo Glauber model and hydrodynamic evolution of small systems.a, Average second (third) order spatial eccentricities, ε2 (ε3), shown as columns for small impact parameter p+Au (red), d+Au (blue), and 3 He+Au (black) collisions as calculated from a MC Glauber model.The second and third order spatial eccentricities correspond to ellipticity and triangularity respectively as depicted by the shapes inset in the bars.b, Hydrodynamic evolution of a characteristic head-on p+Au (top), d+Au (middle), and 3 He+Au (bottom) collision at √ s N N = 200 GeV as calculated by sonic, where the p/d/ 3 He completely overlap with the Au nucleus.From left to right each row gives the temperature distribution of the nuclear matter at four time points following the initial collision at t = 0.The arrows depict the velocity field, with the length of the longest arrow plotted corresponding to β = 0.82.

2 FIG. 2 .
FIG. 2. | Measured vn(pT ) in three collision systems.a, Measurements of v2(pT ) in the 0-5% most central p+Au, d+Au, and 3 He+Au collisions at √ s N N = 200 GeV.A d+Au event from a MC Glauber model is inset with the elliptic symmetry plane angle, ψ2, depicted.b, Measurements of v3(pT ) in the 0-5% most central p+Au, d+Au, and 3 He+Au collisions at √ s N N = 200 GeV.A 3 He+Au event from a MC Glauber model is inset with the triangular symmetry plane angle, ψ3, depicted.Each point in a,b represents an average over pT bins of width 0.2 GeV/c to 0.5 GeV/c; black diamonds are 3 He+Au, blue squares are d+Au, red circles are p+Au.Line error bars are statistical and box error bars are systematic (Methods).

FIG. 3 .
FIG.3.| Measured vn(pT ) in three collision systems compared to models.a, Measured vn(pT ) in the 0-5% most central p+Au collisions compared to models.b, Measured vn(pT ) in the 0-5% most central d+Au collisions compared to models.c, Measured vn(pT ) in the 0-5% most central 3 He+Au compared to models.Each point in a-c represents an average over pT bins of width 0.2 GeV/c to 0.5 GeV/c; black circles are v2, black diamonds are v3.The solid red (dashed blue) curves in a-c represent hydrodynamic predictions of vn from sonic (iEBE-VISHNU).The solid green curves in a-c represent initial-state momentum correlation postdictions of vn from MSTV.

FIG. 4 .
FIG. 4. | Measured v2(pT ) in p+Au and d+Au collisions at the same event multiplicity.Measured v2(pT ) in the 0-5% most central p+Au collisions and 20-40% central d+Au collisions compared to sonic predictions and MSTV post-dictions.Each point represents an average over pT bins of width 0.2 GeV/c to 0.5 GeV/c; blue circles are d+Au, red circles are p+Au.Line error bars are statistical and box error bars are systematic (Methods).The quoted dN ch /dη values are taken from Ref.[36].Blue and red curves correspond to sonic predictions for d+Au and p+Au, respectively.The green curve corresponds to MSTV calculations for 0-5% central p+Au collisions, which the authors state are also applicable to d+Au collisions at the same multiplicity.

TABLE I .
Systematic uncertainties in the v3 measurements as a function of pT in 0-5% central p+Au, d+Au, and 3 He+Au [25] collisions at √ s N N = 200 GeV.

TABLE II .
Calculated p-values between model calculations and data.