Studies of Strange Sea Distribution Functions using Kaons with CLAS12 @ Jlab Fatiha Benmokhtar Duquesne University, Pittsburgh, PA, USA Baryons 2016, Tallahassee, FL, USA F. Benmokhtar, Baryons 2016 1

Flavor contributions to the Nucleon Spin valence « sea= virtual pairs » Our interest is on getting all the flavors! But Special interest on the strange sea. - Why the strangeness  because of its impact on calculations of short distance processes at high energies. F. Benmokhtar, Baryons 2016

-p elastic scattering World Data on S Polarized deep-inelastic inclusive scattering (SMC) -p elastic scattering (E734 BNL) Polarized Semi-Inclusive DIS (HERMES) * 5 flavor tagging * Isoscalar method-> published (2008) then reviewed and published (2014), slightly positive COMPASS: sidis m-NH3 (2010)  compatible with zero. ATLAS results (2012) suggest that at small x the strangeness contribution can be substantially larger than assumed. So far, the results vary widely and the uncertainties are big “Strange quark polarization puzzle” F. Benmokhtar, Baryons 2016

Semi Inclusive DIS Sidis Selection: Hadron Selection:  = E-E’ x = Q2 /(2M  ) y =  /E W2 = M2 - 2M  - Q2 Q2 = 4EE’sin2(θ/2) Hadron Selection: z = Eh /  xF = 2 |p||| / W F. Benmokhtar, Baryons 2016

Measurement of Δq in Semi-Inclusive DIS Select PDFs : q -(x) or q +(x) by changing the orientation of target nucleon spin or helicity of incident lepton beam - Pqh Purity is a conditional probability that a hadron of type h observed in the final state is originated from a struck quark of flavor q in case of unpolarized beam/target. - Dqh is a measure of the probability that a quark of flavor q will fragment into a hadron of type h = fragmentation function

Isoscalar extraction of ΔS: Measure (inclusive) asymmetry A1,d and (sidis) kaon asymmetries A1(K++K-) Extract isoscalar combinations of ΔQ(x) and ΔS(x) Inclusive purities from PDFs (CTEQ6, MRST, GRV…) Kaon purities can be computed from the Kaon multiplicities and the pdfs. F. Benmokhtar, Baryons 2016

Kaon Purities Fit parameters Measure Multiplicities - Using charge symmetry Fit parameters Measure Multiplicities F. Benmokhtar, Baryons 2016

E12‐09‐007 CLAS12 – Jefferson Lab (A-): (H. Avakian, F. Benmokhtar, A. EL Alaoui, K. Hafidi & M. Mirazita) Goal: Measurements of pions and kaons multiplicities and longitudinal double spin asymmetries using SIDIS off hydrogen and deuterium targets. Extract all the flavors! F. Benmokhtar, Baryons 2016

Flavor decomposition E12‐09‐007 CLAS12 : Flavor Decomposition Unpolarized Measurements Polarized Measurements Proton Deuteron Deuteron Proton Measure Multiplicities (π+, π-, π0, K+, K-, Ks0) Measure Multiplicities (π+ + π-, K+ + K-, Ks0) Measure Asymmetries (e-, π+ + π-, K+ + K-, Ks0) Measure Asymmetries (e-, π+, π-, π0, K+, K-, Ks0) Isoscalar Method Extract shape of Extract *Extraction of Δu − Δd to test whether or not the light sea is symmetrically polarized Flavor Decomposition 9 F. Benmokhtar, Baryons 2016 Extract

Jefferson Lab CLAS12 @ 11GeV Wide detector and physics acceptance (current/target fragmentation) High beam polarization 85% High target polarization 85% NH3,ND3 targets Track resolutions: p (GeV/c) 0.003p + 0.001p2  (mr) < 1 (mr) < 3 Lumi > 1035cm-1s-1 F. Benmokhtar, Baryons 2016

A RICH detector is under construction! Replace one or two LTTC with a Ring Imaging CHerenkov GeV/c 1 2 3 4 5 6 7 8 9 10 p/K p/p K/p e/p TOF HTCC EC/PCAL LTCC RICH A RICH detector is under construction! LTCC RICH HTCC LTCC RICH LTCC F. Benmokhtar, Baryons 2016

CLAS12 RICH detector F. Benmokhtar, Baryons 2016

RICH Collaboration F. Benmokhtar, Baryons 2016

Expected precision (Strangeness) Corrections F. Benmokhtar, Baryons 2016

Conclusion: promise of considerable improvement in statistics and the understanding of the strange sea and other flavors contributions to the Nucleon spin. - More flavor separation plots on backup. Thanks! F. Benmokhtar, Baryons 2016

Projections – Deuteron unpolarized data K+ + K- HERMES: 0.2 < z < 0.8 & integrated over Q2 CLAS12: 1.3 < Q2 < 1.6 GeV2 & 0.5 < z <0.6 4. < Q2 < 5. GeV2 & 0.5 < z <0.6 Ks0 F. Benmokhtar, Baryons 2016 16

Projections – Isoscalar Method K+ + K- Ks0 F. Benmokhtar, Baryons 2016

Projections – Flavor decomposition (1) - 10% systematics on asymmetries F. Benmokhtar, Baryons 2016

Projections – Flavor decomposition (2) - 10% systematics on asymmetries F. Benmokhtar, Baryons 2016

E12‐09‐007 update Kawtar Hafidi 1 Goal: Measurements of pions and kaons multiplicities and longitudinal double spin asymmetries using SIDIS off hydrogen and deuterium targets. The experiment will use the CLAS12 spectrometer to detect the scattered electron and the produced hadron in coincidence ■ Extraction of the individual contributions of quarks and anti-quarks to the nucleon spin using the 5-flavor decomposition method. In addition, the isoscalar method will be used to obtain the strange sea contribution ■ Extraction of the unpolarized strange sea shape 0.05<x<0.7, 1<Q^2<9 GeV^2, 0.4<z<0.7 ■ Multiplicity data will provide more constraints to improve the existing fragmentation functions parameterizations ■ Extraction of Δu − Δd to test whether or not the light sea is symmetrically polarized The success of this program relies on the combination of the highly polarized 11 GeV electron beam, the high luminosity and the large acceptance offered by CLAS12. The use of a RICH detector is mandatory for the improvement of particle identification Spokespersons: K. Hafidi, H. Avakian, F. Benmokhtar, A. EL Alaoui, M. Mirazita F. Benmokhtar, Baryons 2016 20 F. Benmokhtar, DNP meeting 2015

Backup slides F. Benmokhtar, Baryons 2016

Jlab 12 GeV experiment: E12-09-007: A. Avakian, F. Benmokhtar, K. Hafidi, A. El-Alaoui and M. Mirazita F. Benmokhtar, Baryons 2016

- Cherenkov angle distributions for 8GeV/c pions tagged by the CERN T9 gas Cherenkov compared with those of kaons and protons. F. Benmokhtar, Baryons 2016

Isoscalar extraction of ΔS Need a longitudinally polarized deuterium target - strange quark in proton and neutron identical - fragmentation simplifies Assumptions: - isospin symmetry between proton and neutron - charge-conjugation invariance in fragmentation Extraction from data of: - inclusive A1d(x,Q2) and kaon A1dK(x,Q2) double spin asymmetries - kaon multiplicities F. Benmokhtar, Baryons 2016

F. Benmokhtar, Baryons 2016

ΔS from SIDIS 1- Five flavor decomposition (Δq) 2-Isoscalar extraction of ΔS F. Benmokhtar, Baryons 2016

Strange Quark Contribution to the Nucleon Properties (in brief) Mass: Hyp -> -N ->  0 to 30 % with big theoretical uncertainties… Longitudinal Momentum: -Study the spectral functions q(x), From unpol DI -Nucleon scattering (NuTeV) . For x <0.1  Difficult to connect with ordinary observable Electromagnetic Form Factors: Parity violation experiments: G0, HAPPEX, PVA4.  Small F. Benmokhtar, Baryons 2016

Kaon Multiplicities Fit parameters Measure Multiplicities - Using charge symmetry Fit parameters Measure Multiplicities F. Benmokhtar, Baryons 2016

Quark helicities contribution to the nucleon spin Inclusive DIS Semi-Inclusive DIS ΔΣ = 0.2 – 0.25 at Q2= 1 GeV2 MS-Bar scheme Δu is large and positive Δd is negative and smaller ΔS ≈ -0.06 ± 0.01 Δu is large and positive Δd is negative and smaller ΔS ≈ 0 and slightly positive Assumptions: SU(3) flavor symmetry in hyperon decay Flavor symmetric sea Quark and anti-quarks of the same flavor can not be distinguished The strange sea can only be separated in terms of first x-moments Need a good knowledge of fragmentation functions The exploitation of the method suffers from “u-quark dominance” Kawtar Hafidi SIDIS kaons @ CLAS12 Probing strangeness in hard processes 10/19/2010 F. Benmokhtar, Baryons 2016

A RICH detector with CLAS12 For forward scattered particles(θ<13deg) with momenta p ~3–8 GeV/c, a proximity imaging method with thin (2cm) aerogel and direct Cherenkov light detection will be used. - For larger incident particle angles of 13<θ<35 and intermediate momenta of p~3–6 GeV/c, the Cherenkov light will be focused by a spherical mirror, undergo two further passes through the thin radiator material and a reflection from planar mirrors before detection. F. Benmokhtar, Baryons 2016

Phys. Rev. D 89, 097101 – Published 30 May 2014 HERMES 2014 HERMES 2008 Phys. Rev. D 89, 097101 – Published 30 May 2014 ATLAS Phys. Rev. Lett. 109, 012001 – Published 5 July 2012 F. Benmokhtar, Baryons 2016