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--- 2015:groups:higgs:pseudoxsecs [2015/06/06 13:54]
frank.tackmann created
+++ 2015:groups:higgs:pseudoxsecs [2015/07/14 08:23] (current)
philippe.gras Added instructions for CERN account
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-====== Discussion on Pseudo Observables/Cross Sections for Higgs Measurements ======
+====== Discussion on Pseudo Observables/Simplified Cross Sections for Higgs Measurements ======
+//If you are interested in contributing please subscribe to the [[https://e-groups.cern.ch/e-groups/EgroupsSearch.do?searchValue=houches-2015-topics-higgs-simplified-xsection|mailing list]]. You will be asked to log in with your CERN account. If you don't have a CERN account, please fill [[https://account.cern.ch/account/Externals/RegisterAccount.aspx|this form]] to create a lightweight account.//
+//This twiki page is closed -- session 2, we welcome your comments, and in particular suggestions on the BSM-motivated regions including proposals for the "BSM jokers" [[2015:groups:pseudoxsecsBSM|here]].//
+//[Update]//: For an overview talk with some more details see [[https://indico.cern.ch/event/399923/session/3/contribution/20/material/slides/0.pdf|here]] (corresponding to 2nd iteration below).
+==== Goal: ====
+Define "simplified cross sections" as general framework for Higgs measurements and combination of decay channels.
+  * Provide "measurement interface" between raw experimental categories and final interpretation.
+  * Can think of these as "differential/fiducial mu" per production channel, but normalized as cross sections (i.e., without dividing by SM predictions)
+  * Ensure long shelf life of experimental measurements
+  * Minimize theory dependence (theory systematics and model dependence) in measurements.
+  * Can then be interpreted in SM (analogous to current mu fits) or different BSM scenarios (Higgs-EFTs or specific models)
+==== Guiding principles for definition of simplified cross sections: ====
+  * Should be reasonably well constrained/measured
+  * Important to think which phase-space regions are important to separate out from the theory side
+    * where are largest theory systematics (e.g. ggF 0jet bin)
+    * BSM sensitivity/interpretation (e.g.  EFT breaks down at high energy).
+== Notes: ==
+  * Does not replace measurement of fiducial/differential cross sections in gammagamma and ZZ
+  * Allows maximizing experimental sensitivity, e.g. can still use MVA-based selections, ...
+    * Still important to ensure that MVAs do not introduce uncontrolled theory systematics (e.g. check which phase space regions get selected)
+  * Some of the (pseudo)observables might also be
+    * limits
+    * asymmetries
+    * continuous parameters for kinematic deviations (e.g. CP odd admixture)
+  * Definition can evolve
+    * Can split into more fine-grained bins once statistics allows (previous measurements remain useful)
+== Specific points for further discussion: ==
+  * Experiments will have to give correlations, need to define how to do the exact "information transfer"
+    * in some cases covariance matrix may not be enough and need full likelihood?
+==== 1st iteration ====
+of possible cross sections (in the following "bins"), to be continued ...
+For 2nd iteration: Reduce number of bins, classify according to importance/feasibility
+== Notes: ==
+  * "ggF-topology", "VBF-topology", ... describe the SM-like kinematic topology, not necessarily only the SM production mode. So one can think of it as using the SM itself as a "simplified kinematic model". (In practice, on the experimental side the corresponding SM processes are used to evaluate and unfold the acceptance corrections.)
+  * everything is meant schematically, all numbers are just for illustration
+  * In the future, can add additional non-SM-like kinematic templates (e.g. CP-odd ggF)
+== ggF-topology ==
+=0j \\
+=1j, separate bin for pTj>~100 GeV (or pTH>~100 GeV) \\
+=2j, separate bin with VBF cuts \\
+ >=3j \\
+  * inputs: gammagamma, ZZ, WW, tautau (for 1j > 100 GeV, 2j VBF and >=3j)
+== VBF-topology ==
+main: mjj >~ 300 GeV (and have some rest 120-300 to not lose any region) \\
+more possibilities: mjj, pTj, Deltaetajj \\
+pTj1 = [0, 100, 200, 300, inf] \\
+some jet-veto-like selection (e.g. pTHjj) \\
++ kinematics measure for non-SM-like continuous shape changes (O(<5) parameters)
+  * inputs: gammagamma, ZZ, WW, tautau, bbbar
+== VH-topology (V -> hadrons) ==
+mjj 70 - 120 GeV \\
+m(VH) = [0, 300, 600, inf] (more ideal from theory side) \\
+or pT(V) = [0, 100, 200, inf] (matches analysis more closely) \\
+and split everything by =0j, >=1j (at first only for high pT(V) or m(VH)) \\
+  * inputs: gammagamma, ZZ
+  * Need to think about how to best deal with the overlap between VBF and VHhad
+== VH-topology (V -> leptons) ==
+keep the Z and W separately: Z->ll, Z->nunu, W->lnu \\
+same bins as for VHhad (need to see how well this works with neutrinos) \\
+  * inputs: bbbar, gamgam, ZZ, WW, tautau
+== gg->ZH-topology ==
+as for VH, likely fewer bins (more relevant for higher pT(V), m(VH)) \\
+== ttH ==
+j, 3j, 4, 5j, 6j \\
++ continuous CP-odd parameter \\
+== bbH ==
+single inclusive cross section bin
+== tHW, tHjq ==
+inclusive and then as few kinematic parameters as possible
+==== 2nd iteration ====
+== Notes: ==
+  * jets are assumed as anti-kt 0.4, |eta|<4-5, pT>=25-30 GeV
+  * bins are exclusive (in the selection, start from the lowest bin on the list)
+  * "ggF-topology", "VBF-topology", ... describe the SM-like kinematic topology, not necessarily only the SM production mode. So one can think of it as using the SM itself as a "simplified kinematic model". (In practice, on the experimental side the corresponding SM processes are used to evaluate and unfold the acceptance corrections.)
+  * explicit numbers are only meant as ball-park numbers
+Proposal for two reduced scenarios, "small" and "medium", trying to take into account feasibility with current statistics, theoretical uncertainties, and sensitivity to BSM.
+== ggF-topology ==
+SMALL\\
+j\\
+ >=1j, split into pTH < = mH, pTH = mH - 200 GeV, pTH > 200 GeV (highest bin for BSM)\\
+ >=2 VBF (mjj, Deltaetajj cuts as for VBF), split into =2 and >=3 by a pTHjj cut\\
+MEDIUM\\
+split  pTH > 200 GeV into 200 GeV - high, and > high\\
+split >=1j to =1j and >=2j (with the pTH splitting)\\
+== VBF-topology ==
+SMALL\\
+rest\\
+ >=2j, with mjj and Deltaetajj cuts, split into =2 and >=3 by a pTHjj cut\\
+"high-q^2" bin (can be replaced by something else BSMy, could be high pTj1)\\
+MEDIUM\\
+allow for continuous parameter to allow for contribution of CP odd coupling
+(interference is probably irrelevant, but could check)\\
+another "BSM joker" (TBD by session 2)\\
+== VH-topology ==
+SMALL\\
+exclusive in ll+nunu, lnu, had\\
+pT(V) = 0 - mH (low) and mH - inf (high)\\
+split high in =0j, >=1j\\
+pT(V) > 200 GeV (for BSM)
+MEDIUM\\
+split ll and nunu\\
+split low pT(V) bin into 0j and >=1j\\
+== gg->VH-topology ==
+same as for VH, if completely degenerate can give the sum of VH and gg->VH
+== ttH ==
+SMALL\\
+incl bin\\
+MEDIUM\\
+split into 0j, >=1j additional jets (with a rather high pT cut, maybe 50-100 GeV?)\\
+add "BSM joker" (to be defined by session 2)
+== bbH ==
+MEDIUM\\
+incl bin
+== tH ==
+MEDIUM\\
+incl bin
-// under construction //

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