1. Ángel Sierra, Pablo Fierro, Irais Bautista and Antonio Ortiz
MC studies: multiplicity dependence of the average pT and its fluctuation
Ángel Sierra, Pablo Fierro, Irais Bautista and Antonio Ortiz
April 23, 2016 1

2. Dynamical Fluctuations (scale-independent approach: integrating over short- and long- range contributions)
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3. Dynamical Fluctuations (scale-dependent approach)
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4. Jet fragments should give us positive correlations with multiplicity
For example, dynamical <pT> fluctiation can give us information about the evolution of the soft and hard component with the event multiplicity.
Jet fragments should give us positive correlations with multiplicity
Particles from difractive processes probably reduces their pT with increasing multiplicity (anti-correlation?)
Underlying event activity increases with the jet pT, this component is therefore expected to give positive correlations
Background events should give no correlations (e.g. isotropic and high multiplicty events?)
Multiplicity increase
(Average pT, per event, increases)
Soft component
Hard component
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5. Different studies can be performed
We know that MC generators reproduce the fluctuations of the average pT as a function of the event multiplicity, we can therefore study the following
Sources of non-statistical correlations
Color reconnection (easy to check in MC)
Multiple partonic interactions
Jets (this will be checked with event shapes and jet finders)
Coulomb attraction (analysis with same ++, -- and +- in low multiplicity and small Delta phi-eta regions?)
Flow (hydrodynamic flow can be checked in EPOS 3) vs. flow-like (CR)
The next slides show some initial studies using MC (Pythia 8.212) and applying cuts on the particle pT (0.15<pT<2 GeV/c)
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6. Simulations
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7. WITH COLOR RECONNECTION
Average transverse momentum
Fluctuations of the average transverse momentum
Bias to high-pT jets fragmenting in low pT particles
Without such a bias
WITH COLOR RECONNECTION
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8. WITH COLOR RECONNECTION
Average transverse momentum
Fluctuations of the average transverse momentum
Héctor
Angel & Pablo
We see these effects in data
(TPCITS08 vs V0M)
WITH COLOR RECONNECTION
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9. WITH COLOR RECONNECTION
Three particle density regions which we explore
Average transverse momentum
Fluctuations of the average transverse momentum
WITH COLOR RECONNECTION
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10. WITHOUT COLOR RECONNECTION
Three particle density regions which we explore
Overall increase of the fluctuation when CR is activated, but w/o CR fluctuations are still not pure statistical (jets!)
Average transverse momentum
Fluctuations of the average transverse momentum
WITHOUT COLOR RECONNECTION
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12. Here we plot the Cm’ distributions:
Which illustrates the behavior of the correlator entering in the definition of the mean pT fluctuations (see next slide).
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13. WITHOUT COLOR RECONNECTION
These events will be studied: check process id, check acceptance effects, check jet content
Here we plot the Cm’ distributions:
Which illustrates the behavior of the correlator entering in the definition of the mean pT fluctuations (see next slide).
WITHOUT COLOR RECONNECTION
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14. Results using ALICE data
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20. To do Compare both systems
Underestand the nature and behavior of C'm in diferent regions