MC Generators for SIDIS and Exclusive Channels Harut Avakian (JLab) 1 H. Avakian, DPWG, Nov 15
Single hadron production in hard scattering x F >0 (current fragmentation) h x F <0 (target fragmentation) x F - momentum in the CM frame Target fragmentation Current fragmentation semi-inclusive exclusive h FF h DA DA h M GPD PDF 1 -1 x F 0 Fracture Functions k T -dependent PDFs Generalized PDFs Wide kinematic coverage of large acceptance detectors allows studies of hadronization both in the target and current fragmentation regions 2 H. Avakian, DPWG, Nov 15
Other factors T. Rogers (INT-2018) Challenges at moderate scales • Non-zero hadron masses •Constituents have non-zero virtuality, mass, etc. •The separation between regions gets squeezed. Low-to-moderate Q opportunities: Access to interesting non-perturbative phenomena Mass effects need to be accounted for Systematic diagnostic tools needed 3 H. Avakian, DPWG, Nov 15
3D structure of the nucleon Non-perturbative distributions in hard scattering GPDs TMDs Wigner Distributions � � � � Fracture Functions unpol. quarks in long. pol. nucleon related to OAM! 4 H. Avakian, DPWG, Nov 15
SIDIS x-section p ┴ � P hT = p ┴ +z k ┴ � e 2 d 2 p ⊥ d 2 k ⊥ δ (2) ( zk ⊥ + p ⊥ − P hT ) f q ( x,k ⊥ ) D q → h ( z,p ⊥ ) F UU,T = x q or q or any representation of structure functions!!! 5 H. Avakian, DPWG, Nov 15
All moments are relevant I. Akushevich et al σ = σ UU + σ cos φ UU cos φ + S T σ sin φ S sin φ S + ..... UT Due to radiative corrections, f -dependence of x-section will get multiplicative R M and additive R A corrections, which could be calculated from the full Born ( s 0 ) cross section for the process of interest σ ehX Rad ( x, y, z, P T , φ , φ S ) → σ ehX ( x, y, z, P T , φ , φ S ) × R M ( x, y, z, P T , φ ) + R A ( x, y, z, P T , φ , φ S ) 0 Due to radiative corrections, f -dependence of x-section will get more contributions •Some moments will modify •New moments may appear, which were suppressed before in the x-section Simplest rad. correction Correction to normalization R ( x, z, φ h ) = R 0 (1 + r cos φ h ) σ 0 (1 + α cos φ h ) R 0 (1 + r cos φ h ) → σ 0 R 0 (1 + α r/ 2) Correction to SSA σ 0 (1 + sS T sin φ S ) R 0 (1 + r cos φ h ) → σ 0 R 0 (1 + sr/ 2 S T sin( φ h − φ S ) + sr/ 2 S T sin( φ h + φ S )) Correction to DSA σ 0 (1 + g λ Λ + f λ Λ cos φ h ) R 0 (1 + r cos φ h ) → σ 0 R 0 (1 + ( g + fr/ 2) λ Λ ) • To get a proper account of radiative corrections the full set of relevant azimuthal moments should be accounted (Bastami et al arXiv:1807.10606 ) • Simultaneous extraction of all moments is important also because of correlations! 6 H. Avakian, DPWG, Nov 15
Radiative SIDIS Akushevich&Ilyichev in progress +….. additional photon can be described by three additional variables: The phase space of the real photon: 7 H. Avakian, DPWG, Nov 15
Event generators for DIS/SIDIS/HEP studies Main classes of event generators: a)Full event generators where sets of outgoing particles are produced in the interactions between two incoming particles and a complete event is generated Applications: attempt to reproduce the raw data understand background conditions estimating rates of certain types of events planning and optimizing detector performances,… b) Specific event generators (single hadron, di-hadron, DVCS…) , where only the final state particles of interest are generated Applications: providing fast tests of analysis procedures with relatively simple integration of different input models. developing analysis frameworks. 1) Providing events with cross section 2) Phase space with realistic x-sections provided as weight factors +unfolding measured data for acceptance and detector resolution effects 3) Easier implementation of Radiative Effects 8 H. Avakian, DPWG, Nov 15
Event generators for DIS/SIDIS/HEP studies https://github.com/JeffersonLab/clasdis-nocernlib Event generators in github: https://github.com/JeffersonLab/inclusive-dis-rad https://github.com/JeffersonLab/dvcsgen Ex.Readme.md …..... self consistent generator with state of art radiative effects Radiative corrections for all relevant processes should be done with MC generating a radiative photon with account of proper SF set involved. 9 H. Avakian, DPWG, Nov 15
Radiative DIS Akushevich et al. http://www.jlab.org/RC/radgen/ For EVA tests a DIS generator developed which works with x-sections, SFs, grids, has radiative effects. DIS cut (E’>2 GeV) Radiative DIS 10 H. Avakian, DPWG, Nov 15
Recovering generated input from reconstructed set Step-II 40Mil generated events (200x200 bins) line N. Sato • Acceptance can be defined using the weighted generator set • Both MCs after reconstruction recover the generated input in most of the kinematics.) 11 H. Avakian, DPWG, Nov 15
Comparing different DIS models filled symbols F 2 /F 2 CJ15 open symbols F 2 /F 2 CJ15 , LT reasonable agreement in most of the relevant kinematics x 12 H. Avakian, DPWG, Nov 15
Standard input for SFs (JavaScript Object Notation for a single hadron production eN->e � X) Table can be generated from any existing program for calculation of SFs for any given set of parameters, final state particles, target nucleon, polarization states in tiny bins. 13 H. Avakian, DPWG, Nov 15
Experiment-Theory interaction Experimentalists measure Theorist come up with some description certain quantities (multiplicity, of the x-section, based on some set of asymmetry, x-section structure functions Observables in form of a table bin# <average kin> | Define procedure to extract parameters observable | <err>stat | defining the involved SFs <err>syst Extract those parameters, based on input from experiment. Normally theory is not dictating the output form (excl. weighted asymmetries) What will be the most efficient format for the data (and metadata)? • Data required for certain analysis may require event by even info • How to store and preserve the data (for unbinned analysis) • Alternative to store full events (all tracks) event level analysis (ELA)? • Should provide easy access for theory 14 H. Avakian, DPWG, Nov 15
3D PDF Extraction and VAlidation (EVA) framework EVA meetings at JLab to finalize SIDIS,DY,e+/e-) Hard Scattering MC goals and coordinate efforts experiments (GEANT, FASTMC,…) QCD Library for event selection Grid operations fundamentals Structure e � hX, e � hhX,.. Function (SF) Radiative x-section SF x-section calculations calculations calculations Data Counts (x-sections, Defined set of 3D PDF and Defined set of multiplicities,….) assumptions FF (models, assumptions parametrizations) Extract 3D PDFs extract Extract x-section SFs Validation of extracted SFs or 3D PDFs (for a given set of assumptions) Development of a reliable techniques for the extraction of 3D PDFs and fragmentation functions from the multidimensional experimental observables with controlled systematics requires close collaboration of experiment, theory and computing 15 H. Avakian, DPWG, Nov 15
Extraction of DIS x-section and acceptance e - • Acceptance can be used to correct distributions for monitoring • DIS output can be generated using input F1,F2 or directly x-sections 16 H. Avakian, DPWG, Nov 15
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