madspace: 2 -> 1 processes with PDFs, one energy and one PDF per beam

docs/source/madevent_to_mg7.rst

@@ -15,7 +15,9 @@ existing scripts keep working. These are ``nevents``, ``gridpack``, ``fixed_ren_
 ``scale``, ``dsqrt_q2fact1``, ``dsqrt_q2fact2``, ``scalefact``, ``bwcutoff``, ``cut_decays``
 and ``use_syst``. The shortcuts ``set lhc``, ``set lep``, ``set fixed_scale``,
 ``set no_parton_cut`` and ``set dynamical_scale_choice HT/n`` work as before, and so does
-``set iseed``. MadEvent draws a random seed for ``iseed = 0``. MG7 does the same for
+``set iseed``. The beam settings ``ebeam``, ``ebeam1``, ``ebeam2``, ``lpp``, ``lpp1``,
+``lpp2``, ``pdlabel``, ``pdlabel1``, ``pdlabel2`` and ``lhaid`` are translated as in the
+table below. MadEvent draws a random seed for ``iseed = 0``. MG7 does the same for
 ``seed = -1`` and treats ``0`` as an ordinary fixed seed, so ``set iseed 0`` is translated.
 All other settings must use their new names.
 
@@ -30,19 +32,21 @@ Beams and PDFs
       - ``run_card.toml``
       - Notes
     * - ``ebeam1``, ``ebeam2``
-      - ``beam.e_cm``
-      - The sum of the two energies. Only symmetric beams are supported.
+      - ``beam.ebeam1``, ``beam.ebeam2``
+      - One energy per beam. With different energies the events are written, and the
+        :math:`\eta` cuts applied, in the lab frame.
     * - ``lpp1``, ``lpp2``
       - ``beam.leptonic``
       - ``false`` for proton beams and ``true`` for lepton beams without PDFs. Other beam
         types, such as elastic photons or antiprotons, are not supported.
     * - ``pdlabel``, ``lhaid``
-      - ``beam.pdf``
+      - ``beam.pdf1``, ``beam.pdf2``
       - The name of the LHAPDF set instead of its id. For example, ``lhaid = 331900`` becomes
-        ``"NNPDF40_lo_as_01180"``.
+        ``"NNPDF40_lo_as_01180"``. ``set beam.pdf`` sets both beams.
     * - ``pdlabel1``, ``pdlabel2``
-      - ``beam.pdf``
-      - MG7 uses one PDF set for both beams.
+      - ``beam.pdf1``, ``beam.pdf2``
+      - One set per beam. A beam without PDF exists only for a lepton collider, as
+        ``beam.leptonic``.
 
 Scales
 ------
@@ -212,8 +216,8 @@ The following MadEvent features have no MG7 equivalent. Settings for them are ig
 * Beam polarization and heavy-ion or equivalent-photon beams: ``polbeam1``, ``polbeam2``,
   ``nb_proton1``, ``nb_proton2``, ``nb_neutron1``, ``nb_neutron2``, ``mass_ion1``,
   ``mass_ion2``, ``ievo_eva``, ``evaorder``, ``eva_xcut``.
-* Different PDFs or fixed factorization scales for the two beams, and the scale
-  parameters ``mue_over_ref``, ``mue_ref_fixed`` and ``fixed_extra_scale``.
+* Fixed factorization scales for the two beams, and the scale parameters
+  ``mue_over_ref``, ``mue_ref_fixed`` and ``fixed_extra_scale``.
 * Cuts that are not a bound on a single observable: ``cutuse = 1``, which accepts an event if
   any of the ordered jet cuts passes, and the vector-boson-fusion cuts ``xetamin`` and
   ``deltaeta``, which require the two hardest jets to lie in opposite hemispheres.

docs/source/run_card.rst

@@ -116,17 +116,22 @@ See :doc:`gridpacks` for details.
 [beam]
 ------
 
-``e_cm`` (``13000.0``)
-    Center-of-mass energy in GeV. Units are accepted, for example ``"13 TeV"``.
+``ebeam1`` (``6500.0``), ``ebeam2`` (``6500.0``)
+    Energy of each beam in GeV, beam 1 moving along :math:`+z`. Units are accepted, for
+    example ``"7 TeV"``. The collision energy is :math:`2\sqrt{E_1 E_2}`. With different
+    energies the events are written, and the :math:`\eta` cuts applied, in this lab frame.
+    ``e_cm`` can still be read and set: ``set e_cm 13 TeV`` sets both beams to 6.5 TeV.
 
 ``leptonic`` (``false``)
-    Treat the beams as leptons: no PDFs are used and the partonic energy equals ``e_cm``.
-    This is set automatically for lepton-collider processes, together with ``e_cm = 1000``
-    and no jet cuts.
-
-``pdf`` (``"NNPDF40_lo_as_01180"``)
-    Name of the LHAPDF set. MG7 tries to download it if it is not installed. The default is
-    the 5-flavor NNPDF 4.0 LO set, which has 100 error members for the PDF variations.
+    Treat the beams as leptons: no PDFs are used and the partonic energy equals the
+    collision energy. This is set automatically for lepton-collider processes, together
+    with 500 GeV beams and no jet cuts.
+
+``pdf1`` (``"NNPDF40_lo_as_01180"``), ``pdf2`` (``"NNPDF40_lo_as_01180"``)
+    Name of the LHAPDF set of each beam. ``set beam.pdf X`` sets both. MG7 tries to
+    download a set that is not installed. The default is the 5-flavor NNPDF 4.0 LO set,
+    which has 100 error members for the PDF variations. With different sets on the two
+    beams the PDF member variations of ``[systematics]`` are dropped.
 
 ``fixed_ren_scale`` (``false``), ``fixed_fact_scale`` (``false``)
     Use the fixed values below instead of the dynamical scale choice. The two switches act

madgraph/iolibs/template_files/mg7/gridpack.py

@@ -342,9 +342,12 @@ def load_systematics(run_card, backends=(), param_card_path=None,
     subproc_args = [
         ms.SubprocessSystArgs.from_json(json.dumps(a)) for a in data["subproc_args"]
     ]
-    nominal_pdf = None
+    nominal_pdf = nominal_pdf2 = None
     if config.has_pdf:
         nominal_pdf = ms.PdfGrid(_locate_pdf_file(data["nominal_grid_file"]))
+        # the second beam's set, recorded only when it differs from the first
+        if data.get("nominal_grid_file2"):
+            nominal_pdf2 = ms.PdfGrid(_locate_pdf_file(data["nominal_grid_file2"]))
     # The mu_R variations always need an alpha_s grid, so a gridpack that does
     # not name one cannot reweight anything -- drop the systematics rather than
     # die here (gridpacks written before the launcher recorded the file for a
@@ -393,7 +396,7 @@ def load_systematics(run_card, backends=(), param_card_path=None,
             ))
     systematics = ms.SystematicsCalculator(
         config, subproc_args, nominal_pdf, nominal_alpha_s,
-        context, matrix_elements, flavor_remap)
+        context, matrix_elements, flavor_remap, nominal_pdf2=nominal_pdf2)
     for warning in systematics.warnings:
         print("WARNING systematics: %s" % warning)
     return systematics