Event-shape and multiplicity dependence of freeze-out radii in pp collisions at $$ \sqrt{s} $$ = 7 TeV
抄録
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>Two-particle correlations in high-energy collision experiments enable the extraction of particle source radii by using the Bose-Einstein enhancement of pion production at low relative momentum <jats:italic>q</jats:italic> ∝ 1/<jats:italic>R</jats:italic>. It was previously observed that in pp collisions at <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \sqrt{s} $$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> </jats:alternatives> </jats:inline-formula> = 7TeV the average pair transverse momentum <jats:italic>k</jats:italic> <jats:sub>T</jats:sub> range of such analyses is limited due to large background correlations which were attributed to mini-jet phenomena. To investigate this further, an event-shape dependent analysis of Bose-Einstein correlations for pion pairs is performed in this work. By categorizing the events by their transverse sphericity <jats:italic>S</jats:italic> <jats:sub>T</jats:sub> into spherical (<jats:italic>S</jats:italic> <jats:sub>T</jats:sub> > 0:7) and jet-like (<jats:italic>S</jats:italic> <jats:sub>T</jats:sub> < 0:3) events a method was developed that allows for the determination of source radii for much larger values of <jats:italic>k</jats:italic> <jats:sub>T</jats:sub> for the first time. Spherical events demonstrate little or no background correlations while jet-like events are dominated by them. This observation agrees with the hypothesis of a mini-jet origin of the non-femtoscopic background correlations and gives new insight into the physics interpretation of the <jats:italic>k</jats:italic> <jats:sub>T</jats:sub> dependence of the radii. The emission source size in spherical events shows a substantially diminished <jats:italic>k</jats:italic> <jats:sub>T</jats:sub> dependence, while jet-like events show indications of a negative trend with respect to <jats:italic>k</jats:italic> <jats:sub>T</jats:sub> in the highest multiplicity events. Regarding the emission source shape, the correlation functions for both event sphericity classes show good agreement with an exponential shape, rather than a Gaussian one.</jats:p>
収録刊行物
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- Journal of High Energy Physics
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Journal of High Energy Physics 2019 (9), 2019-09
Springer Science and Business Media LLC