| Summary: | Heavy and light quarks produced in high-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>p</mi><mi>T</mi></msub></semantics></math></inline-formula> partonic collisions radiate differently. Heavy quarks regenerate their color field, stripped-off in the hard reaction, much faster than the light ones and radiate a significantly smaller fraction of the initial quark energy. This peculiar feature of heavy-quark jets leads to a specific shape of the fragmentation functions observed in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></mrow></semantics></math></inline-formula> annihilation. Differently from light flavors, the heavy quark fragmentation function strongly peaks at large fractional momentum <i>z</i>, i.e., the produced heavy–light mesons, <i>B</i> or <i>D</i>, carry the main fraction of the jet momentum. This is a clear evidence of the dead-cone effect, and of a short production time of a heavy–light mesons. Contrary to propagation of a small <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>q</mi><mover accent="true"><mi>q</mi><mo>¯</mo></mover></mrow></semantics></math></inline-formula> dipole, which survives in the medium due to color transparency, a heavy–light <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Q</mi><mover accent="true"><mi>q</mi><mo>¯</mo></mover></mrow></semantics></math></inline-formula> dipole promptly expands to a large size. Such a big dipole has no chance to remain intact in a dense medium produced in relativistic heavy ion collisions. On the other hand, a breakup of such a dipole does not affect much the production rate of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Q</mi><mover accent="true"><mi>q</mi><mo>¯</mo></mover></mrow></semantics></math></inline-formula> mesons, differently from the case of light <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>q</mi><mover accent="true"><mi>q</mi><mo>¯</mo></mover></mrow></semantics></math></inline-formula> meson production.
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