Reply to ``Comment on `Reevaluation of the parton distribution of strange quarks in the nucleon'''

Reply to “Comment on ‘Reevaluation of the parton distribution of strange quarks in the nucleon’”

E. C. Aschenauer, H. E. Jackson, S. Joosten, K. Rith, G. Schnell, and C. Van Hulse (For the HERMES Collaboration)

Phys. Rev. D 92, 098102 – Published 19 November 2015

Abstract

A Comment on the recently published reevaluation of the polarization-averaged parton distribution of strange quarks in the nucleon using final data on the multiplicities of charged kaons in semi-inclusive deep-inelastic scattering (DIS) is reviewed. Important features of the comparison of one-dimensional projections of the multidimensional HERMES data are pointed out. A test of the leading-order extraction of $x_{B}$ $S (x_{B})$ using the difference between charged-kaon multiplicities is repeated. The results are consistent with leading-order predictions within the uncertainties in the input data, and do not invalidate the earlier extraction of $x_{B}$ $S (x_{B})$ .

Received 19 August 2015

DOI:https://doi.org/10.1103/PhysRevD.92.098102

Authors & Affiliations

E. C. Aschenauer¹, H. E. Jackson², S. Joosten³, K. Rith⁴, G. Schnell^5,6, and C. Van Hulse⁵ (For the HERMES Collaboration)

¹Brookhaven National Laboratory, Upton, New York 11772-5000, USA
²Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843, USA
³Department of Physics, University of Illinois, Urbana, Illinois 61801-3080, USA
⁴Physikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
⁵Department of Theoretical Physics, University of the Basque Country UPV/EHU, 48080 Bilbao, Spain
⁶IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain

Reevaluation of the parton distribution of strange quarks in the nucleon

A. Airapetian et al. (HERMES Collaboration)

Phys. Rev. D 89, 097101 (2014)

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Vol. 92, Iss. 9 — 1 November 2015

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Images

Figure 1
Comparison of the shapes of multiplicities corrected to $4 π$ of charged kaons and pions in semi-inclusive DIS from a deuterium target, as a function of Bjorken $x_{B}$ . The kaon multiplicities are scaled to agree with those of pions in the range of $x_{B}$ where both distributions flatten. Data are plotted at the average $x_{B}$ of each individual $x_{B}$ bin.
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Figure 2
Born space in ( $x_{B}$ , $Q^{2}$ ) corresponding to the multiplicities reported in Ref. [2]. Kinematic regions covered by two data points with similar average kinematics, as discussed in the Comment [3], are superimposed (highlighted slices in either $x_{B}$ or $Q^{2}$ ). Note that the color coding is logarithmic, and that most of the events [ $O (70 %)$ ] in either of the two bins are in fact not shared.
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Figure 3
Left: $K^{'}$ “multiplicities” corrected to $4 π$ of charged kaons in semi-inclusive DIS from a deuterium target, as a function of $x_{B}$ , evaluated with Eq. (4) using MSTW08 (squares), CTEQ6 (upward triangles), NNPDF3.0 (downward triangles), and NNPDF2.3 (full circles) LO PDF sets. Also shown are the LO predictions [e.g., Eq. (5)] using DSS FFs (crosses) or using the high- $x_{B}$ HERMES data to constrain the unfavored $\bar{u}$ and $\bar{d}$ to $K^{+}$ FFs (stars). For both the crosses and stars, $S \int d z D_{S}^{K}$ from Ref. [1] and $Q$ from NNPDF3.0 were used. Note that uncertainties on PDFs or FFs—when available at all—were not propagated, but only total experimental uncertainties. Right: Equation (5) evaluated in the same way as the crosses to the left, but for a range of scaled DSS unfavored nonstrange kaon FFs (using scaling factors from 0 (bottom) to 4 (top) as in Fig. 2 (left) in the Comment [3]). As in the Comment [3], all points were evaluated at the average $Q^{2}$ of each individual $x_{B}$ bin.
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Figure 4
The $Q^{2}$ dependence of the DSS favored $u$ and $\bar{s}$ (scaled by a factor $1 / 7$ ) as well as the unfavored $\bar{u}$ to $K^{+}$ fragmentation functions. Note that for the DSS FF set $D_{\bar{u}}^{K^{+}} = D_{\bar{d}}^{K^{+}}$ . Chosen $Q^{2}$ values correspond to the average $Q^{2}$ of the $x_{B}$ bins in Figs. 3 and 5.
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Figure 5
The scaled charge-difference multiplicities $d N^{K^{diff}} / d N^{DIS} \cdot (5 Q + 2 S) / [4 (u_{v} + d_{v})]$ of charged kaons in semi-inclusive DIS from a deuterium target, as a function of $x_{B}$ , evaluated using various LO PDF sets [MSTW08 (squares), CTEQ6 (upward triangles), NNPDF3.0 (downward triangles), and NNPDF2.3 (circles)], compared with the LO predictions based on solely DSS FFs (crosses) and DSS FFs combined with unfavored kaon FFs constrained using HERMES data at high $x_{B}$ (stars). As in the Comment [3], all points were evaluated at the average $Q^{2}$ of each individual $x_{B}$ bin.
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