Measurement of the W boson rapidity, helicity, and differential cross sections in pp collisions at √(s) = 13 TeV
CDS record for the paper draft: http://cms.cern.ch/cds/SMP-18-012
Detailed record of the paper: http://cms.cern.ch/iCMS/analysisadmin/cadi?ancode=SMP-18-012
Comments from Torino.
Dear Authors and ARC Members, here are the CWR comments from the Torino group. Congratulations to the Authors for the impressive amount of work. This is interesting paper that presents important results. The analysis appears solid and convincing. However, the analysis and results sections are at times difficult to read; it would be great if the Authors could try to make them more concise and if possible clearer. We have made some suggestions to improve it. Please find below our comments divided in type A and B.
TYPE B comments (to the authors)
L30 : a sudden break from the electroweak sector to QCD leaves the reader puzzled. Add a “liaison” phrase to explain the role of W in QCD ?
L153: convoluted sentence. Assuming that “observable sensitive …” refers to both bremsstrahlung and momentum-energy matching, could simplify as:
“Electron identification is based on observables sensitive to bremsstrahlung along the electron trajectory and geometrical and momentum-energy matching between the electron trajectory and the associated supercluster, as well as ECAL shower-shape observables and variables that allow for the rejection of the background arising from random associations of a track and a supercluster in the ECAL”
L214-5: Gaussian function with a floating scale and width –> Gaussian function with floating scale and width [I guess both the scale and the width are floating?]
L170: which dedicated corrections? Add an reference to the section where this is discussed (4.1?)
L174: in the following sentence “Thus the offline electron selection also employs a tight requirement for the charge definition” you want to refer to the electron channel only, or also to the muon channel? Is the charge mis-identification problematic only for the electron channel?
L193-197: obscure
L251: to weight the events in the application sample by εpass/(1 − εpass), to obtain the estimated contribution from the non-prompt lepton background in the signal region.
– this sounds cryptic: why εpass/(1 − εpass)?
L262: The differential agreement in the two-dimensional → what is the “differential agreement” ?
L268-9: the central value of the QCD background is re-scaled by the values derived in this closure test. – I am lost
L297: it's not clear if the MC generates isotropically or has an unknown angular distribution
L340: not sure how Fig 2 should show the cuts for electrons. Perhaps remove “as indicated by Fig 2”
L348: All events above the threshold |YW| = 2.5 are fixed to the prediction from MC – not sure what we mean by 'events fixed to the prediction of the MC'. Likewise in line 350
Fig 1 : what is the origin of the accumulation at 50 GeV ? Perhaps it should be explained in the text
L364-5: each signal process in this measurement corresponds to the underlying generated lepton pT and lepton |η| bin. – I am lost…
L380-1: implementation is the native support of analytic gradients – what is an analytic gradient? and what do we mean by native support?
Figure 3 : horizontal dotted lines should be the same top and bottom
Figure 5,6 : consider showing the unrolled distributions rotated by 90 degrees on a separate page
L411-12: The charge asymmetry, unfolded into |YW| through the ML fit,
– I am not sure what we mean by 'unfolded into |YW|'. Perhaps:
The charge asymmetry, determined as a function of |YW| through the ML fit,
L446: “fake-lepton” : this terminology, while common, is different from what used in Section 5 while explaining background estimation. Either add a definition of “fake-lepton”, or use a consistent terminology with Section 5. Note that “fakes” is defined at L660 in the list of groups of uncertainties, and is used consistently in that context afterwards.
L688-9: These distributions represent the two-dimensional templates, unrolled into one dimension, – not sure what is meant by 'unrolled'. Maybe 'projected'?
L730-2: Two additional bins, 2.5 < |YW| < 2.75 and 2.75 < |YW| < 10 that integrate over the kinematic region in which the detector acceptance is small, are fixed to the expectation from MADGRAPH5 aMC@NLO with a large 30% normalization uncertainty. –> The cross section in the two additional bins, 2.5 < |YW| < 2.75 and 2.75 < |YW| < 10, where the acceptance is small, are fixed to the expectation from MADGRAPH5 aMC@NLO with a large 30% normalization uncertainty. [is this what we mean?]
L778-80: In particular, the agreement of the absolute cross sections between the flavor channels highlights the experimental agreement between the flavors after consideration of all systematic uncertainties.
– not sure what the message of this sentence is.
TYPE A comments (to the LE)
Throughout the paper: I think CMS guidelines advice for the use of the symbol “y”, rather than “\upsilon” for rapidity.
L38: “has to carry” → carries
L40: “being the quark ” add “rather than the anti-quark
L43: become → becomes
L84: two end sections –> two endcap sections
L86-7: coverage provided by the barrel and end detectors —> coverage provided by the barrel and endcap detectors.
L100: Candidate events are selected with single-lepton triggers, with online pT thresholds of 24 GeV for muons and 27 GeV for electrons. For electrons, a higher threshold (up to about 40 GeV) for the level-1 hardware trigger was in place… —> Candidate events are selected with single-lepton triggers, with a level-1 trigger pT thresholds of 24 GeV for muons and 27 GeV for electrons. For electrons, a higher threshold (up to about 40 GeV) was in place…
L105: muons and require a careful —> muons and requires a careful
L119: L125 dash not necessary “boson p_t”
L125: the treatment of the theoretical uncertainties regarding the boson-pT spectrum … is large enough to cover the difference … —> the theoretical uncertainties regarding the boson-pT spectrum … are large enough to cover the difference …
L136: very long sentence. Consider to add a break. ..tracks in the muon detectors to reconstruct these individual particles and to determine quality criteria which are used to select the particles used in the distributions of the final state observables. —> ..tracks in the muon detectors to reconstruct these individual particles. The algorithm also determine quality criteria which are used to select the particles in the distributions of the final state observables.
L139: “within the geometrical acceptance”: add “of the muon spectrometer”
L147: suggest to hyphen “pileup-corrected ratio”
L173: suppressed as much as possible → reduced to a minimum
L174: Consider adding a comma after “Thus” at the beginning of the sentence.
L186: In order to maximize the rejection efficiency for these events they are rejected if additional leptons, identified … —> In order to maximize the rejection efficiency, these events are rejected if additional leptons, identified ..
L191: “both … as well as” → “both … and”.
L191: as this is the dominant → and these are the dominant
L202: The lepton efficiency for each step is determined with respect to the previous step. A technique called tag-and-probe is used in which the efficiency for each step is measured for MC simulation —> The lepton efficiency for each step is determined with respect to the previous step, using a technique called tag-and-probe applied over MC simulation
L217-8: a simple ratio of passing probes over all probes. –> a simple ratio of the number of passing probes over that of all probes.
L221-2: The alternative background is modeled by a function which models the phase space in the invariant mass for two leptons satisfying the minimum pT criteria applied. –> The alternative background representation is a function that models the phase space in the invariant mass for two leptons satisfying the minimum pT criteria applied.
L228: “kinematics for which” → “kinematics. Therefore, ” (or, if this is not what was meant, reformulate appropriately)
L247-8: This QCD enriched sample, that is disjoint to the signal sample –> This QCD enriched sample, which is independent of the signal sample
L253: The εpass is computed –> The efficiency εpass is computed
L258 which modifies the sample composition by changing the fractions of gluon- or quark-induced jet. —> which modifies the fractions of gluon- or quark-induced jet in the sample.
L262: M_T requirement → m_T requirement
L262-5: .. with lepton η and pT, being within 20% for both the electron and muon channel in the whole kinematic range and better than 10% for lepton pT > 30 GeV. –> ..with lepton η and pT; it is better than 20% for both the electron and muon channels in the whole kinematic range and better than 10% for lepton pT > 30 GeV.
L266-7: The level of agreement in the background dominated region is used as an estimate of the normalization systematic of this process in the signal extraction described in Sec. 7. –> The level of agreement in the background dominated region is taken as an estimate of the systematic uncertainty in the normalization of this process.
L280: background from W → eν where –> background from W → eν, where [comma]
L281: charge is considered –> charge, is considered
L284-5: templates in the charged lepton kinematic observables of pTl versus ηl –> templates in the charged lepton kinematic observables pTl and ηl
L two lines below Eq (2) the lepton refers –> the term lepton refers
L: one line down (and elsewhere): Eq. 1 –> Eq. (1)
L294: are related to the coefficients Ai of Eq. 2 by A0 ∝ f0 –> are related to the coefficients Ai of Eq. (2), with A0 ∝ f0
L301: “a reweighting procedure” → “the reweighting procedure”, since this procedure is already introduced at L297
L306: by reweighting of the extracted helicity fractions fi. –> by reweighting the extracted helicity fractions fi.
L306: Distributions for pWT and |YW| are shown –> Distributions of pWT and |YW| are shown
L309: behave the same –> behave in the same way
L310: Their production cross section is equal at |YW| = 0, –> Their production cross sections are equal at |YW| = 0,
L310: but the WL component –> but that of the WL component
L311: whereas the WR component decreases monotonically with higher |YW|. –> whereas that of the WR component decreases monotonically with |YW|.
L315: components paired –> components, paired
L316: states results –> states, results
L325: and the three helicity components. –> and for the three helicity components. [is this what we mean?]
L326: constructing … templates → I guess we should add “from the MC sample described above”. I don't think we said explicitly that the templates are from MC yet
L327: An example of a 2D templates –> An example of a 2D template
L328: The blue template is obtained from WR produced –> The blue template is obtained from events with a WR produced [is this what we mean?]
L329: the red template from WR produced –> the red template from WR events produced
L330: the green template from WL produced between 2.00 and 2.25 in |YW|. –> the green template from WL events with 2.00 < |YW|<2.25.
L349: due to the rapid loss –> because of the rapid loss
L352: for each charge and left and right polarizations. –> for each charge and polarization.
L353+1: The double differential W boson cross sections, –> The double differential W boson production cross sections,
L362: pTl versus lepton ηl, –> pTl versus ηl,
L375-6: The treatment of the backgrounds and the systematic uncertainties remains –> The treatment of the backgrounds and the systematic uncertainties remain
L397: true cross section, ⃗σ(⃗θ) and –> true cross section, ⃗σ(⃗θ), and [please insert comma]
L402-3: allows for the direct measurement of the constraints that are being set by the data on every nuisance parameter. –> allows for the direct measurement of the constraints set by the data on every nuisance parameter.
L407-8: The fit to the data is performed simultaneously for the two charge categories and to the three helicity states. –> The fit to the data is performed simultaneously for the two charge categories and the three helicity states.
L413: previous measurements performed at LHC, which are performed –> previous measurements at LHC, which are performed [repetition]
L413-6: In the CDF collaboration measurement [10] the W boson charge asymmetry was unfolded in |YW |, but inclusively in the W boson helicity state. –> In the CDF collaboration measurement [10], the W boson charge asymmetry was extracted as a function of |YW |, but not separately for the W boson helicity.
L417: If the distribution is integrated over pTl the results can be compared –> If the distribution is integrated over pTl, the results can be compared
Eq 8. If sigma is double-differential it should be squared
L418: hardon→ hadron
L418: Similarly, when integrating over |η|l, the A(pTl ) can be found. –> Similarly, when integrating over |η|l, A(pTl ) can be found.
L428: They are allowed to change the overall normalization of the process by the quoted value –> They are allowed to change the overall normalization of the process [not sure what we mean by quoted value]
L430: the lepton pT versus lepton η bins. –> the lepton pT, η bins.
L435: i.e. to change –> i.e., to change [comma, to be consistent with US usage in the rest of the paper]
L447: uncorrelated to the others. –> uncorrelated with the others.
L455: dependency on the lepton η and pT. –>
dependence on the lepton η and pT.
L456: A further check has been carried out, by computing –> A further check has been carried out by computing [no comma]
L456-458: commas misplaced; suggestion: “Based on these checks, an additional… is introduced … in the muon case. No additional uncertainty is introduced for electrons.”
L459: Another shape uncertainty is applied to cover for the uncertainty in the extraction of the QCD multijet efficiency εpass. –> The uncertainty in the extraction of the QCD multijet efficiency εpass is quantified as follows. [to avoid repetition]
L488: using the Z boson standard candle. –> using Z boson events.
L486: The first fit is to a MC template –> The first fit is with a MC template
L487: the second to a functional form made of a Breit-Wigner lineshape –> the second with a functional form consisting of a Breit-Wigner lineshape
L498: an eventual constraint of it –> its constraint
L514: from a few per mille –> from about 0.1% [per mille is not used in Am English]
L521: These systematics are considered –> These uncertainties are considered
L527: estimated using a set of Z → e+e− from unbiased triggers –> estimated using a set of Z → e+e− events from unbiased triggers
L537: This uncertainty ranges from 2% at low electron pT, and is up to 10% –> This uncertainty ranges from 2% at low electron pT to 10%
L540: The probability of a charge flip for a muon –> The probability of mistakenly assigning the muon charge
L542: in the estimate of the charge flips in Z → e+e− –> in the estimate of wrong charge assignment in Z → e+e−
L560: is minimal up to pTl < 35 GeV, however, for pTl > 35 GeV –> is minimal up to pTl < 35 GeV; however, for pTl > 35 GeV
L567: in the region of low pWT , a region in which fixed-order –> in the region of low pWT , where fixed-order [repetition]
L572: Namely, the uncertainties –> The uncertainties
L575: cross section measurement an uncorrelated –> cross section measurement, an uncorrelated [comma]
L619: using a Breit-Wigner assumption for the invariant mass –> using a Breit-Wigner assumption for the invariant mass distribution
L624: has been produced –> is produced? [present tense elsewhere]
L625: interfacing a QCD NLO MC program to either PYTHIA 8 or PHOTOS. –> and is interfaced to either PYTHIA 8 or PHOTOS. [is this what we mean?]
L640: An uncertainty is assigned to the limited size of the MC sample –> An uncertainty is assigned to reflect the limited size of the MC sample
L645: A summary of the systematic uncertainties applied is shown in Table 2 –> A summary of the systematic uncertainties is shown in Table 2
L688: for the positive (negative) charges. –> for the positive (negative) charge.
L709: is also done independently. –> is also carried out/performed independently.
L710-2: The tests done on the application of a common εpass to positive and negative charges separately show that this systematic uncertainty can be considered 100% correlated between the two charges for each lepton flavor. –> The systematic uncertainty on εpass can be considered 100% correlated between the two charges for each lepton flavor.
L713: The statistical uncertainties in the efficiency correction factors are implemented uncorrelated –> The statistical uncertainties in the efficiency correction factors are taken as uncorrelated
L714: and uncorrelated among the channels –> and among the channels
L777: due to –> thanks to
L818-21: A differential measurement of the W boson cross sections, measured as a function of the W boson rapidity, |YW|, and for the two charges separately, W+ → l+ν and W− → l−ν ̄, is presented by the CMS Collaboration. –> A differential measurement of the W boson cross sections as a function of the W boson rapidity, |YW|, and for the two charges separately, W+ → l+ν and W− → l−ν ̄, is presented.