We have observed muon pairs with effective masses in the range 7<~Mμμ<~11 GeV/c2 produced by 300- and 400-GeV protons incident on a Cu target at Fermilab. The production cross section per nucleon, dσdMμμ, for 400-GeV incident protons is found to fall from 1 × 10−36 cm2/(GeV/c2) at Mμμ=7.7 GeV/c2 to 2.7 × 10−38 cm2/(GeV/c2) at Mμμ=11.2 GeV/c2. We find that a significant fraction of the observed direct single muons come from high-mass dimuons.
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We have measured the inclusive production of massive dimuons (7<~Mμμ<~11 GeV/c2) by 200-, 300-, and 400-GeV protons incident on Cu in order to check whether the dimensionless cross section Mμμ3[dσdMμμdy]y=0 is a function of Mμμ2s alone, where s is the square of the c.m. energy. The results support the scaling hypothesis.
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Differential cross sections as a function of transverse momentum are presented for the production at ∼90° (in the c.m. system) of π±, K±, p, and p¯ in p-nucleus collisions at incident proton energies of 200 and 300 GeV.
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Measurements of the invariant cross section Ed3σd3p are presented for the production of hadrons (π, K, p, and p¯) at large transverse momentum (p⊥) by 200-, 300-, and 400-GeV protons incident on H2, D2, Be, Ti, and W targets. The measurements were made at a laboratory angle of 77 mrad, which corresponds to angles near 90° in the c.m. system of the incident proton and a single nucleon at rest. The range in p⊥ for the data is 0.77≤p⊥≤6.91 GeV/c, corresponding to values of the scaling variable x⊥=2p⊥s from 0.06 to 0.64. For p−p collisions, the pion cross sections can be represented in the region x⊥>35 by the form (1p⊥n)(1−x⊥)b, with n=8 and b=9. The ratio of π+ to π− production grows as a function of x⊥ to a value larger than 2 at x⊥≳0.5. The ratios of the production of K+ and protons to π+ and of K− and antiprotons to π− also scale with x⊥ for p−p collisions. The K±, p, and p¯ fitted values for n and b are given. Particle ratios are also presented for D2, Be, Ti, and W targets and the dependences on atomic weight (A) are discussed.
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We have measured, as a function of transverse momentum (p⊥), the invariant cross section Edσd3p for the production of π±, K±, p, p¯, d, and d¯ in proton collisions with a tungsten (W) target at incident proton energies of 200, 300, and 400 GeV. The measurements were made in the region of 90° in the c.m. system of the incident proton and a single nucleon at rest. Measurements were also made with 300-GeV protons incident on Be, Ti, and W targets of equal interaction length. These p-nucleus measurements, which show a strong dependence on atomic number at high p⊥, were used to extract effective proton-nucleon cross sections by extrapolation to atomic number unity. At large values of the scaling variable x⊥=2p⊥s, where s is the square of the c.m. energy, the pion data are found to be well represented by the expression (s)−ne−ax⊥, with n=11.0±0.4 and a=36.0±0.4. x⊥<0.35, where similar measurements have been made at the CERN ISR, our data are in good agreement with the ISR data.
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We have observed muons produced directly in Cu and W targets by 300-GeV incident protons. We find a yield of muons which is approximately a constant fraction (0.8·10−4) of the pion yield for both positive and negative charges and for transverse momenta between 1.5 and 5.4 GeV/c.
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The ratios of K+, K−, p, and p¯ yields to pion yields at transverse momenta (p⊥) ranging from 0.77 to 6.91 GeV/c arepresented for 200-, 300-, and 400-GeV p−p and 400-GeV p−d collisions. The dependences of the particle ratios on p⊥ and the scaling variable x⊥=2p⊥s are discussed.
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We have measured the production of π+ and π− in 200-, 300-, and 400-GeV p−p and 400-GeV p−d collisions for transverse momenta (p⊥) ranging from 0.77 to 7.67 GeV/c. At large values of x⊥=2p⊥s, where s is the c.m. energy, we have fitted the p−p data to the form A(1−x⊥)bp⊥−n; we obtain n=8.2±0.5 for π+ and 8.5±0.5 for π−. At x⊥>0.3 the π+π− ratio in p−p collisions rises appreciably with increasing x⊥ whereas the π+π− ratio obtained from the difference of p−d and p−p cross sections is ∼ 1.0 at all x⊥.
Axis error includes +- 0.0/0.0 contribution (5 AND 10//(C//).
Axis error includes +- 0.0/0.0 contribution (5 AND 10//(C//).
Axis error includes +- 0.0/0.0 contribution (5 AND 10//(C//).
We present measurements from the PHENIX experiment of large parity-violating single spin asymmetries of high transverse momentum electrons and positrons from $W^\pm/Z$ decays, produced in longitudinally polarized $p$$+$$p$ collisions at center of mass energies of $\sqrt{s}$=500 and 510~GeV. These asymmetries allow direct access to the anti-quark polarized parton distribution functions due to the parity-violating nature of the $W$-boson coupling to quarks and anti-quarks. The results presented are based on data collected in 2011, 2012, and 2013 with an integrated luminosity of 240 pb$^{-1}$, which exceeds previous PHENIX published results by a factor of more than 27. These high $Q^2$ data provide an important addition to our understanding of anti-quark parton helicity distribution functions.
Longitudinal single-spin asymmetries, $A_L$, for the 2011 and 2012 data sets (combined) spanning the entire $\eta$ range of PHENIX ($\left|\eta\right|<0.35$), for the 2013 data set separated into two $\eta$ bins, and for the combined 2011-2013 data sets.
We present direct photon-hadron correlations in 200 GeV/A Au+Au, d+Au, and p+p collisions, for direct photon pT from 5–12 GeV/c, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in d+Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in Au+Au compared to p+p and d+Au. As the momentum fraction decreases, the yield of hadrons in Au+Au increases to an excess over the yield in p+p collisions. The excess is at large angles and at low hadron pT and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.
Per-trigger yield of hadrons associated to direct photons in Au+Au collisions for direct photon $p_T$ 5-9 GeV/$c$, compared with p+p baseline, in various $\xi$ bins.
Per-trigger yield of hadrons associated to direct photons in d+Au collisions for direct photon $p_T$ 7-9 GeV/$c$, compared with p+p baseline, in various $\xi$ bins.
Integrated away-side $\gamma_{dir}$-h per-trigger yields of Au+Au, d+Au, and p+p, as a function of $\xi$.
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