Montret%2C J.C
nucl-ex
Max results
Sort by Reverse order

Showing 10 of 450 results

Measurement of Lepton and Pion Pair Production in Photon - Photon Collisions at Dci

Courau, A. ; Falvard, A. ; Haissinski, J. ; et al.
Phys.Lett.B 96 (1980) 402-406, 1980.
Inspire Record 153776 DOI 10.17182/hepdata.49087

We report a photon-photon experiment performed at the Orsay storage rings. 300e + e − , μ + μ − and π + π − pairs produced with low invariant masses have been observed. For each event, one or both protons have been tagged at a very small angle. The γγ→μ + μ − and γγ→π + π − cross-sections have been measured near threshold, the γγ→e + e − process being used as a normalization. The observed invariant mass distribution is compared to theoretical calculations for each of the three processes. The μ + μ − data are in good agreement with QED predictions. The π + π − cross-section, in our experimental acceptance, is somewhat larger than the one expected from the Born terms only.

0 data tables match query

Lepton and Pion Pair Production in $\gamma \gamma$ Collisions Measured Near the Threshold at Dci

Courau, A. ; Falvard, A. ; Haissinski, J. ; et al.
Nucl.Phys.B 271 (1986) 1-20, 1986.
Inspire Record 232808 DOI 10.17182/hepdata.38240

This paper reports a complete analysis of data taken at DCI to measure lepton and pion pair production close to the threshold in two-photon processes: e + e − → e + e − (e + e − , μ + μ − , π + π − ). Preliminary results have been previously published including one-half of the total statistics. Final results presented here are in good agreement with QED for lepton pair production. The measured cross section for pion pair production is twice as large as that expected from Born terms only — a two standard deviation effect.

0 data tables match query

Charged hadron multiplicity fluctuations in Au+Au and Cu+Cu collisions from sqrt(s_NN) = 22.5 to 200 GeV

The PHENIX collaboration Adare, A. ; Adler, S.S. ; Afanasiev, S. ; et al.
Phys.Rev.C 78 (2008) 044902, 2008.
Inspire Record 785509 DOI 10.17182/hepdata.143616

A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV, and Cu+Cu collisions sqrt(s_NN) = 22.5, 62.4, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for non-dynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon p+p data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. An analysis of Negative Binomial Distribution fits to the multiplicity distributions demonstrates that the heavy ion data exhibit weak clustering properties.

2 data tables match query
Figure 3a-1

The mean from the NBD fit as a function of $N_{part}$ for 200 GeV Au+Au collisions over the range 0.2 < $p_T$ < 2.0 GeV/$c$.

Figure 3a-2

The mean from the NBD fit as a function of $N_{part}$ for 62.4 GeV Au+Au collisions over the range 0.2 < $p_T$ < 2.0 GeV/$c$.


Measurements of Dihadron Correlations Relative to the Event Plane in Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV

The STAR collaboration Agakishiev, H. ; Aggarwal, M.M. ; Ahammed, Z. ; et al.
Chin.Phys.C 45 (2021) 044002, 2021.
Inspire Record 872067 DOI 10.17182/hepdata.102351

Dihadron azimuthal correlations containing a high transverse momentum ($p_T$) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to p+p and d+Au collisions. The modification increases with the collision centrality, suggesting a path-length or energy density dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20-60%) Au+Au collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV as a function of the trigger particle's azimuthal angle relative to the event plane, $\phi_s=|\phi_t-\psi_{\rm EP}|$. The azimuthal correlation is studied as a function of both the trigger and associated particle $p_T$. The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (ZYAM), are described. The correlation results are first discussed with subtraction of the even harmonic (elliptic and quadrangular) flow backgrounds. The away-side correlation is strongly modified, and the modification varies with $\phi_s$, with a double-peak structure for out-of-plane trigger particles. The near-side ridge (long range pseudo-rapidity $\Delta\eta$ correlation) appears to drop with increasing $\phi_s$ while the jet-like component remains approximately constant. The correlation functions are further studied with subtraction of odd harmonic triangular flow background arising from fluctuations. It is found that the triangular flow, while responsible for the majority of the amplitudes, is not sufficient to explain the $\phi_s$-dependence of the ridge or the away-side double-peak structure. ...

981 data tables match query
data table 22

flow background with upper flow systematic uncertainty Au+Au 20-60%, 3<p_{\text{T}}^{(t)}<4 GeV/c, 1<p_{\text{T}}^{(a)}<2 GeV/c, slice 2

data table 583

flow background with lower flow systematic uncertainty Au+Au 20-60%, 4<p_{\text{T}}^{(t)}<6 GeV/c, slice 5

data table 584

flow background with lower flow systematic uncertainty Au+Au 20-60%, 4<p_{\text{T}}^{(t)}<6 GeV/c, slice 0

More…

Coherent diffractive photoproduction of $\rho^{0}$ mesons on gold nuclei at RHIC

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.C 96 (2017) 054904, 2017.
Inspire Record 1515028 DOI 10.17182/hepdata.101354

The STAR Collaboration reports on the photoproduction of $\pi^+\pi^-$ pairs in gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair. These pion pairs are produced when a nearly-real photon emitted by one ion scatters from the other ion. We fit the $\pi^+\pi^-$ invariant mass spectrum with a combination of $\rho$ and $\omega$ resonances and a direct $\pi^+\pi^-$ continuum. This is the first observation of the $\omega$ in ultra-peripheral collisions, and the first measurement of $\rho-\omega$ interference at energies where photoproduction is dominated by Pomeron exchange. The $\omega$ amplitude is consistent with the measured $\gamma p\rightarrow \omega p$ cross section, a classical Glauber calculation and the $\omega\rightarrow\pi^+\pi^-$ branching ratio. The $\omega$ phase angle is similar to that observed at much lower energies, showing that the $\rho-\omega$ phase difference does not depend significantly on photon energy. The $\rho^0$ differential cross section $d\sigma/dt$ exhibits a clear diffraction pattern, compatible with scattering from a gold nucleus, with 2 minima visible. The positions of the diffractive minima agree better with the predictions of a quantum Glauber calculation that does not include nuclear shadowing than with a calculation that does include shadowing.

5 data tables match query
Figure 5 a

The ratio $|B/A|$ of amplitudes of nonresonant $\pi^+\pi^-$ and $\rho^0$ mesons in the present STAR analysis.

Figure 5 b

The ratio $|B/A|$ of amplitudes of nonresonant $\pi^+\pi^-$ and $\rho^0$ mesons in the previous STAR analysis, Phys. Rev. C 77 034910 (2008).

Figure 5 c

The ratio $|C/A|$ of amplitudes of $\omega$ and $\rho^0$ mesons.

More…

System size dependence of associated yields in hadron-triggered jets

The STAR collaboration Abelev, B.I. ; Aggarwal, M.M. ; Ahammed, Z. ; et al.
Phys.Lett.B 683 (2010) 123-128, 2010.
Inspire Record 817691 DOI 10.17182/hepdata.102091

We present results on the system size dependence of high transverse momentum di-hadron correlations at $\sqrt{s_{NN}}$ = 200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like correlation yields at small angular separation ($\Delta\phi\sim0$, $\Delta\eta\sim0$) for all systems and centralities. Previous measurements have shown that the away-side yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will provide important constraints on medium density profile and energy loss model parameters.

8 data tables match query
Figure 1 a

Di-hadron correlations in $\Delta\phi$ for small $|\Delta\eta|$ ($|\Delta\eta|<0.7$) and large ($0.7<|\Delta\eta|<1.7$), scaled to match small $|\Delta\eta|$ at large $\Delta\phi$.

Figure 1 b

Subtracted distributions for di-hadron correlations in $\Delta\phi$ for small $|\Delta\eta|$ ($|\Delta\eta|<0.7$) minus large ($0.7<|\Delta\eta|<1.7$), scaled to match small $|\Delta\eta|$ at large $\Delta\phi$.

Figure 1 c

Subtracted distributions for di-hadron correlations in $\Delta\eta$.

More…

Growth of Long Range Forward-Backward Multiplicity Correlations with Centrality in Au+Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV

The STAR collaboration Abelev, B.I. ; Aggarwal, M.M. ; Ahammed, Z. ; et al.
Phys.Rev.Lett. 103 (2009) 172301, 2009.
Inspire Record 819318 DOI 10.17182/hepdata.102090

Forward-backward multiplicity correlation strengths have been measured for the first time with the STAR detector for Au+Au and $\textit{p+p}$ collisions at $\sqrt{s_{NN}}$ = 200 GeV. Strong short and long range correlations are seen in central (0-10%) Au+Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short range correlations are observed in 40-50% Au+Au collisions. The results are in agreement with predictions from the Dual Parton and Color Glass Condensate models.

0 data tables match query

Pseudorapidity dependence of particle production and elliptic flow in asymmetric nuclear collisions of $p$$+$Al, $p$$+$Au, $d$$+$Au, and $^{3}$He$+$Au at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Adare, A. ; Aidala, C. ; Ajitanand, N.N. ; et al.
Phys.Rev.Lett. 121 (2018) 222301, 2018.
Inspire Record 1684475 DOI 10.17182/hepdata.136476

Asymmetric nuclear collisions of $p$$+$Al, $p$$+$Au, $d$$+$Au, and $^{3}$He$+$Au at $\sqrt{s_{_{NN}}}=200$ GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production $dN_{\rm ch}/d\eta$ in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow $v_{2}$ over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.

1 data table match query
Figure 3a

Midrapidity charged hadron $dN_{ch}/d\eta$ per participating quark pair ($N_{qp}$/2) as a function of the number of participating quarks ($N_{qp}$).


Low-momentum direct photon measurement in Cu$+$Cu collisions at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Adare, A. ; Afanasiev, S. ; Aidala, C. ; et al.
Phys.Rev.C 98 (2018) 054902, 2018.
Inspire Record 1672473 DOI 10.17182/hepdata.143521

We have measured direct photons for $p_T<5~$GeV/$c$ in minimum bias and 0\%--40\% most central events at midrapidity for Cu$+$Cu collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The $e^{+}e^{-}$ contribution from quasi-real direct virtual photons has been determined as an excess over the known hadronic contributions in the $e^{+}e^{-}$ mass distribution. A clear enhancement of photons over the binary scaled $p$$+$$p$ fit is observed for $p_T<4$ GeV/$c$ in Cu$+$Cu data. The $p_T$ spectra are consistent with the Au$+$Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the $p$$+$$p$ baseline are 285$\pm$53(stat)$\pm$57(syst)~MeV/$c$ and 333$\pm$72(stat)$\pm$45(syst)~MeV/$c$ for minimum bias and 0\%--40\% most central events, respectively. The rapidity density, $dN/dy$, of photons demonstrates the same power law as a function of $dN_{\rm ch}/d\eta$ observed in Au$+$Au at the same collision energy.

0 data tables match query

Dielectron Azimuthal Anisotropy at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{NN}}} = 200$ GeV

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.C 90 (2014) 064904, 2014.
Inspire Record 1280745 DOI 10.17182/hepdata.96269

We report on the first measurement of the azimuthal anisotropy ($v_2$) of dielectrons ($e^{+}e^{-}$ pairs) at mid-rapidity from $\sqrt{s_{_{NN}}} = 200$ GeV Au+Au collisions with the STAR detector at RHIC, presented as a function of transverse momentum ($p_T$) for different invariant-mass regions. In the mass region $M_{ee}\!<1.1$ GeV/$c^2$ the dielectron $v_2$ measurements are found to be consistent with expectations from $\pi^{0}$, $\eta$, $\omega$ and $\phi$ decay contributions. In the mass region $1.1\!<M_{ee}\!<2.9$ GeV/$c^2$, the measured dielectron $v_2$ is consistent, within experimental uncertainties, with that from the $c\bar{c}$ contributions.

3 data tables match query
Figure 22 (exp. data)

The $p_T$-integrated dielectron $v_2$ as a function of $M_{ee}$ in minimum-bias Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.

Figure 22 (hadron data)

The $v_2$ of hadrons $\pi$, $K$, $p$, $\phi$ and $\Lambda$ in minimum-bias Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV for the $\pi^0$ mass region.

Figure 22 (sim. data)

The $p_T$-integrated dielectron $v_2$ as a function of $M_{ee}$ in minimum-bias Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, expected from the decays of $\pi^0$, $\eta$, $\omega$ and $\phi$ and from the $car{c}$ contribution.