plans for the first jet paper

Plans for the first Jet Paper

PWG04 August 24th 2009

Christian Klein-Bösing for the PWG04 Task Force

A Short, Early Paper on Charged Jet Reconstruction in p+p?

• Want a maximum of statistics– Statistical precision– Systematic studies

• Depend on understanding of high pT tracking – High pT spectra needed first

• But even if the paper will be not “short” or “early” the following should give you an idea of the key points

PWG04 08.2009 Christian Klein-Bösing 2

Not in the timescale of a few weeks

Title


Inclusive Jet Production and Jet Fragmentation in p+p collisions at 7 TeV/10 TeV

Measured with Charged particles in the ALICE Experiment

Beam Energy/Luminosity

PWG04 08.2009 4

7 TeV p+p 10 TeV p+p

Here only MB events, luminosity more relevant when triggering, (But pileup effects depend on luminosity and bunch pattern).109 ≈ 20 d × 60% × 1 kHz

Christian Klein-Bösing

PYTHIA8 simulation + fastjet (R = 0.7)

Rough Abstract


Figures and Tables

• Fig. 1: Response matrix– MC all vs. MC charged– MC charged vs. rec

• Fig. 2:– Fragmentation function (for charged jet)– Comparison to MC and MLLA

• Fig. 3:– Jet spectrum, corrected up to charged jet energy– Unfolded to total jet energy (for different cuts in z of

the leading jet)PWG04 08.2009 Christian Klein-Bösing 6

Fig. 1

• Response Matrix– Emphasize the two levels of

corrections to reconstructed jets

– Charged track jet → charged particle jet → all particle jet


MC

(all

R =

0.4)

MC

(ch.

R =

0.4

)

MC (ch. R = 0.4)

Rec (R = 0.4)

Fig. 2

• Bias of the charged jet reconstruction– Reduced when using dijets

(TODO)

• Compare to different fragmentation models– PYTHIA (string)– HERWIG (cluster)– Also differ in UE– TODO

• At low ξ comparable to calculations (e.g. MLLA) without corrections?– Influence of UE– TODO

• pT,jet > 40 GeV most relevant for comparison with Pb+PbPWG04 08.2009 Christian Klein-Bösing 8

Leading jet fragmentation for R = 0.4 (LHC09a1-3)

Fig. 3


• Raw spectrum corrected for detector effects (charged jet spectrum)

• Fully corrected total jet spectrum

• Different subsamples of jets corrected to full– Different leading

particle z (TODO)

Tables

• Table 1:– Examples for reconstructed momentum shift and

smear due to:• Limited Cone radius• Charged to neutral• MC to reconstruction

• Table 2:– Systematic uncertainties


TODO

Rough Layout


What Needs to Be Done

– Systematic uncertainties • Jet Momentum scale checks• Flavour dependence, biases (cuts on jet shapes)

– Corrections• Revisit unfolding procedure: variable bin size, regularization• Underlying event in multiple collisions

– High pT QA• cannot rely on jet spectrum if single particle spectra are not understood

– Connection to MB data → coordinate QA– Sharpen focus on fragmentation

• Comparison to generators (i.e. PYTHIA: Lund Fragmentation, HERWIG cluster fragmentation) and theory

– Analysis note

PWG04 08.2009 12Christian Klein-Bösing

Momentum Scale

• Induced by JF– Cone radius/R-parameter

• Bias

– Algorithms– Can be studied with data

alone• Correlations• Average energy in certain

“trigger-bin” compared to mean momentum

• Should be symmetric in η-φ: otherwise acceptance effects

– 2D correlation TODO

• Also handle on UE contribution

• Induced by reconstruction– QA, high pT spectra


Charged particles correlated with leading jet axis

High pT QA: Cuts


Improved cut on1/pT uncertainty (relative)

loose cuts

loose cuts +rel pT

error

B. Bathen

People from the PWG4 Task Force

• Jet Spectrum– Unfolding: CKB, Ydalia Delgado

• Jet Finders– FastJet: S. Jangal, M. Estienne, J. Thäder, O. Busch– Deterministic Annealing: D. Perrino

• Di-jets: D. Perrino• Fragmentation function: B. Bathen, V. Roman• Jet shape/topology: S. Pochybova. L. Molnar• Underlying event: A. Abrahantas, E. Lopez, S. Valero, A. Agosc• High pT QA: G. Barros (M. Munhoz), M. Verweij (M. van

Leeuwen), B. Bathen

PWG04 08.2009 15Christian Klein-Bösing

plans for the first jet paper

Documents