Insights into Forward Suppression Mechanisms in pA Energy Scan
"Analysis of pA energy scans reveals the interplay between saturation and e-loss suppression mechanisms, impacting RpA forward suppression. The Cronin peak diminishes at higher energy/rapidity, offering crucial insights into nuclear dynamics."
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Presentation Transcript
Energy Scan in pA Yuri Kovchegov The Ohio State University
CGC Prediction Our analysis shows that as energy/rapidity increases the height of the Cronin peak decreases. Cronin maximum gets progressively lower and eventually disappears. Corresponding RpA levels off at roughly at Toy Model! RpA energy / rapidity increases (Kharzeev, Levin, McLerran, 02) k / QS Kharzeev, Yu. K., K. Tuchin, 03; Albacete, Armesto, Kovner, Salgado, Wiedemann, 03; Baier, Kovner, Wiedemann, 03. At high energy / rapidity RpA at the Cronin peak becomes a decreasing function of both energy and centrality.
RdAu at different rapidities RdAu RCP central to peripheral ratio BRAHMS Collaboration nucl-ex/0403005 CGC prediction of suppression was confirmed!
Rd+Au at forward and backward rapidities PHENIX data, nucl-ex/0411054
More Recent Data STAR data shows even stronger suppression at rapidity of 4.0, strengthening the case for CGC. (figure from nucl-ex/0602011)
A CGC-Inspired Model RdAu pT RCP p from D. Kharzeev, Yu. K., K. Tuchin, hep-ph/0405045, where we construct a model based on above physics + add valence quark contribution T
pA Energy Scan The above effects should diminish and turn into Cronin at higher x. Thus one would expect less suppression in RpA at lower sqrt{s} from saturation physics. Conversely, e-loss mechanism should become stronger at lower sqrt{s}, perhaps simply because a lower-energy parton loses a larger fraction of energy.
E-loss prediction 1.5 RpAu p0 in p+Au min. bias, y = 3 Initial state energy loss effect only Opposite trend from saturation 1 0.5 s = 100 GeV s = 200 GeV s = 500 GeV 0 0 1 2 3 4 5 6 7 8 9 10 pT (GeV) Zhongbo Kang
Conclusions pA energy scan could help distinguish (or understand the interplay) between saturation and eloss suppression mechanisms in RpA forward suppression. Possible theoretical problems: either formalism may break down at lower energy.
