tie CCFM equatjon F Hautmann: Giuseppe Marchesini Memorial - - PowerPoint PPT Presentation

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tie CCFM equatjon F Hautmann: Giuseppe Marchesini Memorial - - PowerPoint PPT Presentation

Jun 30, 2023 96 likes •537 views

GGI Giuseppe Marchesini Memorial Conference Florence, May 2017 F Hautmann Pino and high-energy QCD: tie CCFM equatjon F Hautmann: Giuseppe Marchesini Memorial Conference, GGI , May 2017 1 The CCFM papers Theoretical introduction - this talk

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

GGI Giuseppe Marchesini Memorial Conference

F Hautmann Pino and high-energy QCD: tie CCFM equatjon Florence, May 2017

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

The CCFM papers

Theoretical introduction - this talk Comparisons with experiment – Hannes Jung's talk

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

CCFM and the high-energy QCD landscape – circa 1990

Confdence in theoretical QCD predictions for hard processes not only due to asymptotic freedom but also due to methods to compute systematically large radiative contributions: – collinear parton radiation and renormalization group evolution Dokshitzer; Altarelli-Parisi; Gribov-Lipatov – soft gluon radiation and the role of infrared singularities Dokshitzer-Diakonov-Troyan; Parisi-Petronzio; Mueller; Bassetto-Ciafaloni-Marchesini What becomes of this in the high-energy regime? (relevant to SSC, LHC, HERA colliders . . . ) Note: something must change . . . - fxed t, high s asymptotics! Balitski-Fadin-Kuraev-Lipatov

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

Soft-gluon coherence

The CCFM approach: what does soft-gluon coherence look like in the high-energy (multi-Regge) kinematics

  • Recall eikonal insertion currents:
  • Color coherence effect:

Bassetto-Ciafaloni-Marchesini

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

CCFM: coherence in the high-energy limit

Longitudinal momenta exchanged along the initial-state decay chain become small: x << 1 Internal emissions non-negligible Yet, current is factorizable at high energy!

> J depends on transverse momentum transmitted down the chain

→ TMD (or unintegrated) matrix elements and parton density functions (→ see present-day “TMDs”) > virtual corrections imply, besides Sudakov form factors, modified branching probabilities (→ “parton-shower” MC)

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

Exclusive evolution equation

  • Returns the Balitski-Fadin-Kuraev-Lipatov (BFKL) anomalous dimension

in the inclusive limit for x → 0

  • Incorporates angular ordering and soft-gluon radiation with leading logarithmic

accuracy to all orders in the strong coupling for x → 1 Ciafaloni Catani-Fiorani-Marchesini

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

Space-like Anomalous Dimensions at N → 0

The CCFM equation contains the dominant (BFKL) gluon anomalous dimensions given by Power series expansion: Next-to-leading corrections at N → 0 computed in the subsequent decade. Camici-Ciafaloni; Fadin-Lipatov; Catani-H

N - moment conjugate to ln s

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

Application to Shower Monte Carlo Event Generators

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

CCFM-based Monte Carlo Event Generators

SMALLX (Marchesini and Webber 1991, 1992) CASCADE (Jung and Salam 2001; Jung et al. 2010) LDCMC (Gustafson, Lonnblad and Miu, 2002; Lonnblad and Sjodahl, 2005) UPDFevolv (Jung, Taheri-Monfared and H, 2014) DIPSY (Gustafson, Lonnblad et al. 2011, 2015)

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

OUTLOOK CCFM contributions affect both scaling violation in inclusive structure functions structure of the associated fnal states: jet multiplicities and angular correlations predictions of fnal- states observables at the LHC and future colliders recent determinations

  • f TMD parton density

functions from DIS data

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

Applying CCFM to LHC physics: vector boson + jets fjnal states

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

Applying CCFM to LHC physics: vector boson + jets fjnal states

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

As a conclusion . . .

An early CCFM Monte Carlo simulation Marchesini and Webber,

  • Nucl. Phys. B349 (1991) 617

discussed with Pino at Cortona Theory Meeting and Gran Sasso Summer Institute, 1994

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F Hautmann: Giuseppe Marchesini Memorial Conference, GGI, May 2017

. . . a study of soft-gluon resolution scale in QCD evolution equations Jung, Lelek, Radescu, Zlebcik & H, arXiv:1704.01757

  • highlights the role
  • f angular ordering

in predicting the transverse momentum from the initial-state shower

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