Measurement of Jet Fragmentation in PbPb and pp Collisions at $\sqrt{s_{NN}}= 2.76$ TeV
<p>The jet fragmentation function of inclusive jets with transverse momentum <inline-formula><mml:math><mml:msub><mml:mi>p</mml:mi><mml:mi mathvariant="normal">T</mml:mi></mml:msub></mml:math></inline-formula> above <inline-formula><mml:math><mml:mn>100</mml:mn><mml:mrow><mml:mspace width="0.28em"/><mml:mtext>GeV</mml:mtext><mml:mo>/</mml:mo><mml:mi>c</mml:mi></mml:mrow></mml:math></inline-formula> in PbPb collisions has been measured using reconstructed charged particles with <inline-formula><mml:math><mml:msub><mml:mi>p</mml:mi><mml:mi mathvariant="normal">T</mml:mi></mml:msub></mml:math></inline-formula> above <inline-formula><mml:math><mml:mn>1</mml:mn><mml:mrow><mml:mspace width="0.28em"/><mml:mtext>GeV</mml:mtext><mml:mo>/</mml:mo><mml:mi>c</mml:mi></mml:mrow></mml:math></inline-formula> in a cone of radius 0.3 around the jet axis. A data sample of PbPb collisions collected in 2011 at a nucleon-nucleon center-of-mass energy of <inline-formula><mml:math><mml:mrow><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:msub><mml:mrow/><mml:mi mathvariant="italic">NN</mml:mi></mml:msub></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>2.76</mml:mn><mml:mspace width="0.28em"/><mml:mtext>TeV</mml:mtext></mml:mrow></mml:math></inline-formula> corresponding to an integrated luminosity of <inline-formula><mml:math><mml:mn>150</mml:mn><mml:mrow><mml:mspace width="0.28em"/><mml:mi>μ</mml:mi><mml:msup><mml:mi mathvariant="normal">b</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> is used. The results for PbPb collisions as a function of collision centrality and jet transverse momentum are compared to reference distributions based on <inline-formula><mml:math><mml:mi mathvariant="italic">pp</mml:mi></mml:math></inline-formula> data collected at the same center-of-mass energy in 2013, with an integrated luminosity of <inline-formula><mml:math><mml:mn>5.3</mml:mn><mml:mrow><mml:mspace width="0.28em"/><mml:msup><mml:mtext>pb</mml:mtext><mml:mrow><mml:mo>−</mml:mo><mml:mtext>1</mml:mtext></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula>. A centrality-dependent modification of the fragmentation function is found. For the most central collisions, a significant enhancement is observed in the PbPb/<inline-formula><mml:math><mml:mi mathvariant="italic">pp</mml:mi></mml:math></inline-formula> fragmentation function ratio for charged particles with <inline-formula><mml:math><mml:msub><mml:mi>p</mml:mi><mml:mi mathvariant="normal">T</mml:mi></mml:msub></mml:math></inline-formula> less than <inline-formula><mml:math><mml:mn>3</mml:mn><mml:mrow><mml:mspace width="0.28em"/><mml:mtext>GeV</mml:mtext><mml:mo>/</mml:mo><mml:mi>c</mml:mi></mml:mrow></mml:math></inline-formula>. This enhancement is observed for all jet <inline-formula><mml:math><mml:msub><mml:mi>p</mml:mi><mml:mi mathvariant="normal">T</mml:mi></mml:msub></mml:math></inline-formula> bins studied.</p>
arXiv_1406.0932.pdf
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