Chung-Wen Kao Chung-Yuan Christian University Kaon multiplicities of Semi-inclusive DIS and the fragmentation functions Chung-Wen Kao Chung-Yuan Christian University 2018.11 .13. QNP 2018 Tsukuba, Japan

Collaboration and Reference In Collaboration with Nam Seung-il (PKU, Korea) Dong-Jing Yang, Fu-Jiun Jiang (NTNU, Taiwan) Wen-Chen Chang (AS, Taiwan) This talk is based on the following works: (1) Nam Seung-il, CWK, Phys. Rev .D85, 034023(2012) (2) Nam Seung-il, CWK, : Phys.Rev.D85, 094023(2012) (3) Dong Jing Yang, Fu-Jiun Jaing, CWK, Nam Seung-il: Phys. Rev D87,097004. (2013) (4) Dong Jing Yang, Fu-Jiun Jaing, CWK, Nam Seung-il: arXiv 1407.4453 (5) Dong Jing Yang, Fu-Jiun Jaing, Wen-Chen Chang, CWK, Nam Seung-il: Phys. Lett. B 755(2016) 393

How to extract Fragmentation functions?

SIDIS using deuteron target Charge Conjugation of fragmentation functions Why deuteron ?

SIDIS off deuteron target p: proton, n: neutron

SIDIS using deuteron target Assume PDFs are charge symmetric:

SIDIS using deuteron target DQ>>DS

HERMES Data of Pion multiplicity

Kaon Multiplicity

HERMES Kaon Data A. Airapetian et al. (HERMES Collaboration), Phys. Rev. D 448 89, 097101 (2014).

Pion and kaon multiplicities For pion and kaon multiplicities of SIDIS off the deuteron target: Combine the HERMES data of kaon and DSS07 Fragmentation functions, the strange quark PDF was extracted. Phys. Rev. D 89, 097101 (2014)

Phys.Lett. B755 (2016) 393-402

Constrains on A and B Since S(x)>0, Q(x)>0, then S(x)/Q(x) is positive! At fixed x and Q2 : Note that the values of and are independent of x!

Choices of FFs

HKNS (LO) HKNS (NLO) DSS (LO) DSS (NLO) 5.NJL-Jet Model 6.Nonlocal Chiral Quark Model 7.AKK08 8.SMKA 9.DSEHS

HKNS (LO) HKNS (NLO) DSS (LO) DSS (NLO) 5.NJL-Jet Model 6.Nonlocal Chiral Quark Model 7.AKK08

NLO fitting of SIDIS

A game need two players….

COMPASS and HERMES The data pointes are taken at different Q2 values compared with HERMES data. Phys.Lett. B767 (2017) 133-141

COMPASS and HERMES HERMES COMPASS

COMPASS and HERMES

DSS 2017 fragmentation functions Phys.Rev. D95 (2017) no.9, 094019 , already have 27 citations.

DSS 2017 fragmentation functions

DSS 2017 fragmentation functions

DSS 2017 fragmentation functions

DSS 2017 fragmentation functions

DSS 2017 fragmentation functions

Our Puzzle over DSS17 If DSS17 can describe both of HERMES and COMPASS kaon multiplicities well, then the two sets of data surely are compatible. However, the simple plot shows otherwise. So what’s going on? Maybe the difference of two sets of data is indeed due to the different Q2?

Test of DSS17 at HERMES and COMPASS kinematics Using DSS17 Apply DSS17 with MMHT and NNPDF at (x, Q2) of HERMES data points and COMPASS, we find the theoretical results of both should be close. The effect of Q2 evolution is not enough to explain the difference between two data sets.

Kaon multiplicity Using DSS17

Check HERMES data K+

Check HERMES data K- Error! It should be 𝛼=0.38 𝛼=0.07 𝛼=0.02 𝛼=0.00

Log to Log & Linear to Linear: Fit well?

MK+(x, Q2) and MK-(x, Q2) Red point: usual integral method Blue cross: integrate z by HERMES method Black point: HERMES For positive and negative kaon, The PDFXFF values are higher than The experimental values.

Charged Kaon Multiplicity Similar check on COMPASS kinematics is needed.

Three regions Phys.Lett. B766 (2017) 245-253 by M.Boglione, J.Collins, L.Gamberg, J.O.Gonzalez-Hernandez, T.C.Rogers, N.Sato, LO cross section: PDF X FF

Is it the reason of the serious inconsistency between pion and kaon multiplicities? How to prove or falsify it?

Summary and outlook Is DSS17 good as they claimed? Can one extract the strange PDFs from the current SIDIS data? Is there tension between COMPASS and HERMES data of SIDIS? Is there tension between the pion and kaon multiplicities? Is the contribution of the central region able to explain the difference between HERMES and COMPASS data?

Two data sets of SIDIS cause many confusions, but two cups of ice cream are just perfect!