HERMES Multiplicities

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The HERMES multiplicities of charged pions and kaons from semi-inclusive DIS on the proton and the deuteron represent a unique high-precision multi-dimensional data set that will significantly enhance our understanding of the fragmentation of quarks into final-state hadrons.

The full data set consists of a large amount of data files due to the multitude of binnings and projections. Find your way using the filters below to locate and download the files you are looking for.

A. Airapetian et al, Phys. Rev. D 87 (2013) 074029

Browse Data » Read Publication » Preprint » Download All Data »

Important information

  • In general, only the bins where z > 0.2 should be used. This excludes the lowest two z-bins for the "z-3D" configuration and the lowest z-bin for all other configurations. The bins below z < 0.2 are included only for technical reason (to control for the model dependence of the smearing-unfolding procedure).
  • The data points above z > 0.8 should be treated with caution, as they lie in the region where the fractional contribution from exclusive processes becomes sizable.
  • Due to the unfolding procedure, the different bins are statistically correlated. To correctly treat this correlation, the statistical covariance matrix, also provided with the database, should be used. Note that these covariance matrices only relate to the statistical uncertainty.
  • The systematic uncertainties should be treated as point-to-point uncertainties.
  • The multiplicities are integrated quantities, where both numerator and denominator are integrated separately over the full space within each kinematic bin. A simple evaluation at the average kinematics can lead to misleading results. This is especially important as the different configurations of the multiplicities are not topologically equivalent, as illustrated in the figure on the right. The figure compares the phase space covered for a bin from the z-Q2 (blue) and z-x (red) binnings with the very similar values for their average kinematics. A full explanation can be found in Phys.Rev. D92 (2015) no.9, 098102 .
  • The data files include the average kinematics within each bin for illustrative purposes only. Note that those for the inclusive variables, x and Q2, have been calculated from the full measured inclusive DIS sample.
2D Distribution of inclusive events as a function of x and Q2

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Info

  • Read this before using these data.
  • Use the filter menu to restrict the displayed results to your selection criteria. The 'What' menu allows for quick switching between multiplicity results and various derived quantities. For an explanation of the differences between the available multiplicity versions, see the about section.
  • The download button next to the relevant results yields a tarball of the data. Or you can use the dropdown menu to obtain the separate files for the π⁺, π⁻, K⁺ and K⁻ multiplicities, as well as their covariance matrices.
  • The systematic uncertainties of the multiplicities for different particles and targets is highly correlated. This should be taken into account when calculating derived quantities. Because of this, the average Ph⊥ distributions, hadron charge asymmetry, kaon-to-pion ratio and target asymmetries with correctly propagated systematic uncertainty can also be found below.
  • Data format and binning information can be found here.
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Format and binning info

File name structure

hermes.(TARGET.)BINNING.(PROJECTION.)OPTION.WHAT.list.gz
  • TARGET: Either proton or deuteron. Blank in case of the target asymmetries.
  • BINNING: Can be z-3D, zpt-3D, zQ2-3D zx-3D or zxpt-3D. The binning codes are defined below in the binning subsection.
  • PROJECTION: Blank in case of the 3D data without projection, or VARIABLE-proj for projected data. For example, z-proj for a 1D projection versus z, or zx-proj for a 2D projection versus x in z slices.
  • OPTION: Results with the vector meson contribution subtracted are labelled vmsub, results without this correction are labelled no-vmsub.
  • WHAT:
    • Multiplicity files are labelled mults_PARTICLE (for example: mults_piplus).
    • The covariance matrices for the multiplicities are labelled covmat_mults.
    • Target asymmetry files are labelled asymm_PARTICLE (for example: asymm_piplus).
    • The covariance matrices for the target asymmetries are labelled covmat_asymm.
    • ...

Binning

The smearing-unfolding method to correct for QED radiative effects, limited geometric acceptance and finite detector resolution constrains the minimum granularity in all variables, allowing us to pursuit five different specialized binnings. This way, the widest possible range of use-cases can be accomodated.

  1. High resolution in z.
  2. High resolution in Ph⊥ with z slices.
  3. High resolution in x with z and Ph⊥ slices.
  4. High resolution Q2 with z and Ph⊥ slices.
  5. Balanced binning in x, z and Ph⊥.

High resolution in z

  • Name: z-3D
  • Profile: x: 2 / z: 10 / Ph⊥: 5
  • Use for: The projection versus z, and for analyses that benefit from the full binning profile.
  • Edges:
    Variable Edges
    Q2 [GeV2] > 1
    x 0.023 - 0.085 - 0.6
    z 0.1 - 0.15 - 0.2 - 0.25 - 0.3 - 0.4 - 0.5 - 0.6 - 0.7 - 0.8 - 1.1
    Ph⊥ [GeV] 0.0 - 0.1 - 0.3 - 0.45 - 0.6 - 1.2

High resolution in Ph⊥ with z slices

  • Name: zpt-3D
  • Profile: x: 2 / z: 6 / Ph⊥: 9
  • Use for: The projection versus Ph⊥, The projection versus z and Ph⊥, and for analyses that benefit from the full binning profile.
  • Edges:
    Variable Edges
    Q2 [GeV2] > 1
    x 0.023 - 0.085 - 0.6
    z 0.1 - 0.2 - 0.3 - 0.4 - 0.6 - 0.8 - 1.1
    Ph⊥ [GeV] 0.0 - 0.1 - 0.2 - 0.3 - 0.4 - 0.5 - 0.6 - 0.7 - 0.8 - 1.2

High resolution in x with z slices

  • Name: zx-3D
  • Profile: x: 9 / z: 6 / Ph⊥: 4
  • Use for: The projection versus x, The projection versus x and z, and for analyses that benefit from the full binning profile.
  • Edges:
    Variable Edges
    Q2 [GeV2] > 1
    x 0.023 - 0.04 - 0.055 - 0.075 - 0.1 - 0.14 - 0.2 - 0.3 - 0.4 - 0.6
    z 0.1 - 0.2 - 0.3 - 0.4 - 0.6 - 0.8 - 1.1
    Ph⊥ [GeV] 0.0 - 0.3 - 0.5 - 0.7 - 1.2

High resolution in Q2 with z slices

  • Name: zQ2-3D
  • Profile: Q2: 9 / z: 6 / Ph⊥: 4
  • Use for: The projection versus Q2, The projection versus Q2 and z, and for analyses that benefit from the full binning profile.
  • Edges:
    Variable Edges
    Q2 [GeV2] 1 - 1.25 - 1.5 - 1.75 - 2.0 - 2.25 - 2.5 - 3.0 - 5.0 - 15.0
    x 0.023 - 0.6
    z 0.1 - 0.2 - 0.3 - 0.4 - 0.6 - 0.8 - 1.1
    Ph⊥ [GeV] 0.0 - 0.3 - 0.5 - 0.7 - 1.2

Balanced binning in x, z and Ph⊥

  • Name: zxpt-3D
  • Profile: x: 6 / z: 8 / Ph⊥: 7
  • Use for: Analysis that benefit from a balanced full binning profile.
  • Edges:
    Variable Edges
    Q2 [GeV2] > 1
    x 0.023 - 0.047 - 0.075 - 0.12 - 0.2 - 0.35 - 0.6
    z 0.1 - 0.2 - 0.25 - 0.3 - 0.375 - 0.475 - 0.6 - 0.8 - 1.1
    Ph⊥ [GeV] 0.0 - 0.15 - 0.25 - 0.35 - 0.45 - 0.6 - 0.8 - 1.2

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sylvester.joosten@gmail.com