Correlations of event activity with hard and soft processes in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>p</mml:mi><mml:mo>+</mml:mo><mml:mtext>Au</mml:mtext></mml:mrow></mml:math> collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>200</mml:mn></mml:mrow></mml:math> GeV at the RHIC STAR experiment
Abstract
With the STAR experiment at the BNL Relativistic Heavy Ion Collider, we characterize $\sqrt{{s}_{NN}}=200\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$ $p+\text{Au}$ collisions by event activity (EA) measured within the pseudorapidity range $\ensuremath{\eta}\ensuremath{\in}[\ensuremath{-}5,\ensuremath{-}3.4]$ in the Au-going direction and report correlations between this EA and hard- and soft-scale particle production at midrapidity $(\ensuremath{\eta}\ensuremath{\in}[\ensuremath{-}1,1])$. At the soft scale, charged particle production in low-EA $p+\text{Au}$ collisions is comparable to that in $p+p$ collisions and increases monotonically with increasing EA. At the hard scale, we report measurements of high transverse momentum $({p}_{\mathrm{T}})$ jets in events of different EAs. In contrast with the soft particle production, high-${p}_{\mathrm{T}}$ particle production and EA are found to be inversely related. To investigate whether this is a signal of jet quenching in high-EA events, we also report ratios of ${p}_{\mathrm{T}}$ imbalance and azimuthal separation of dijets in high- and low-EA events. Within our measurement precision, no significant differences are observed, disfavoring the presence of jet quenching in the highest 30% EA $p+\text{Au}$ collisions at $\sqrt{{s}_{NN}}=200\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$.