Low-mass vector-meson production at forward rapidity in $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low-mass vector-meson, $\omega$, $\rho$, and $\varphi$, production through the dimuon decay channel at forward rapidity ($1.2<|y|<2.2$) in $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$. The differential cross sections for these mesons are measured as a function of both $p_T$ and rapidity. We also report the integrated differential cross sections over $1<p_T<7\mathrm{GeV}/c$ and $1.2<|y|<2.2$: $d\sigma /dy(\omega +\rho \to \mu \mu )=80\pm 6(\mathrm{stat})\pm 12(\mathrm{syst})\mathrm{nb}$ and $d\sigma /dy(\varphi \to \mu \mu )=27\pm 3(\mathrm{stat})\pm 4(\mathrm{syst})\mathrm{nb}$. These results are compared with midrapidity measurements and calculations.

Figure 1

The unlike-sign dimuon invariant mass spectra before background subtraction (solid black points), after subtracting mixed-events background (empty red triangles) and after subtracting like-sign background (empty blue circles).

Figure 2

The ${\chi }_{\text{vtx}}^2$ distributions for the nonresonance mass region (red), and signal ($J/\psi$) mass region (blue). The unlike-sign pairs are shown in panel (a) while the like-sign pairs are shown in panel (b). In each panel, the histograms are normalized to the total number of events.

Figure 3

The unlike-sign dimuon invariant mass spectrum (solid red points) and the background spectrum (empty blue circles) normalized using the first normalization method in panel (a), and using the second normalization method in panel (b). The insert in panel (b) shows the muon arms acceptance and reconstruction efficiency.

Figure 4

Raw unlike-sign dimuon spectra (solid black circles) along with normalized background (empty blue circles) separated by ${\chi }_{\text{vtx,}\text{cut}}^2$ in panel (a). Panel (b) shows the normalized background spectrum fitted with a fourth-order polynomial. Panels (c) and (d) show the fitted spectra with (left) and without (right) background subtraction.

Figure 5

The $A{ϵ}_{\text{rec}}$ as a function of rapidity ($x$ axis) and $p_T$ ($y$ axis) for $\omega$.

Figure 6

(Top) $p_T$-dependent differential cross section vs $p_T$ of $\omega +\rho$ at rapidity, $1.2<|y|<2.2$. The error bars represent the statistical uncertainties, and the gray shaded band represents the quadratic sum of type-B systematic uncertainties. The data are compared with the pythia atlas-csc, default and prugia-11 tunes and phojet. (Bottom) Ratio between data and models.

Figure 7

(Top) $p_T$-dependent differential cross section vs $p_T$ of $\varphi$ at rapidity, $1.2<|y|<2.2$. The error bars represent the statistical uncertainties, and the gray shaded band represents the quadratic sum of type-B systematic uncertainties. The data are compared with the pythia atlas-csc, default and perugia-11 tunes and phojet. (Bottom) Ratio between data and models.

Figure 8

(Top) $p_T$-dependent differential cross sections of $\omega$ at rapidity, $|y|<0.35$ [2]. The data are compared with the pythia atlas-csc, default and perugia-11 tunes and phojet. (Bottom) Ratio between data and models.

Figure 9

(Top) $p_T$-dependent differential cross sections of $\varphi$ at rapidity, $|y|<0.35$ [2]. The data are compared with the pythia atlas-csc, default and perugia-11 tunes and phojet. (Bottom) Ratio between data and models.

Figure 10

Rapidity dependent differential cross section of $\omega +\rho$ (a) and $\varphi$ (b) along with previous PHENIX results [2] summed over the $p_T$ range, $1<p_T<7\mathrm{GeV}$. The error bars represent the quadratic sum of the statistical uncertainties and type-A systematic uncertainties, and the gray shaded band represents the quadratic sum of type-B systematic uncertainties. The data are compared with the pythia atlas-csc and perugia-11 tunes and phojet.

Figure 11

$N_{\varphi }/(N_{\omega }+N_{\rho })$ as a function of $p_T$. The error bars represent the quadratic sum of the statistical uncertainties and type-A systematic uncertainties, and the gray shaded band represents the quadratic sum of type-B systematic uncertainties.