Using the tag and mistag rates that we have now, I have calculated the predicted number of W+soft dilepton events in the 1 fb-1 sample.  The calculation is slightly different for the same and opposite flavor dilepton cases. We will show the dielectron case as the same-sign example.

The notation used is as follows

• e=electron, m=muon
• l=light, h=heavy
• j=W+jets, DY=Drell Yan
• R21(a,b) = N(a+b)/N(b) [from MC]

Below is the different flavor case.

The results are below.

Continue reading Number of predicted and observed dilepton events in 1 fb-1 →

We use the fit results below and apply additional DY muon rejection by cutting on events with muon triggers and:

• m(trigger,soft muon)<5 GeV
• 9<m(trigger,soft muon)<10 GeV with opposite charge (upsilon rejection)
• 80<m(trigger,soft muon)<100 GeV with opposite charge (Z rejection)
• emfr(soft lepton jet)>0.8 and only 1 track w/ pT>1 in jet cone (radiative DY rejection)

TCE+1 soft electron

Continue reading Fixed Single Soft Lepton Stacks →

In the post before the previous one, I showed all the soft lepton fits using 3 components.  Most of the fits did not converge.  At the time, Scott suggested that this was because the templates did not use the high luminosity MC and thus had holes in it.  I added the high lumi MC to the templates and there were still convergence problems.  The solution was found by using the data-based mistag shape for the light template rather than W+jets MC.  The corresponding fits are below.  Note that the chisquare is not a real goodness of fit statistic because this is an event-by-event multidimensional fit.

Continue reading Fixed Soft Lepton Fits →

Using the results of the 3 component fit below, we make stacked histograms for the exclusive single lepton bin.

Continue reading 3 Component Single Soft Lepton Stacks →

I thought the fits would perform better if I combined the bottom and charm templates.  I also set the amount of Drell-Yan to 0 in the soft electron fits because it didn’t seem necessary to use it there.  We expect less Drell-Yan because in the soft electrons because the second leg will be soft, nearly collinear with the trigger electron, and therefore knocked out by the trigger electron jet removal.  Here are the results.

The soft muon results with f(heavy)=0.5 are suspicious because that is the initial value of the parameter

As was done for the soft muons earlier, I compare the shapes of the pTrel and d0 distributions for soft electrons in the TCE-triggered sample in MC and mistagged data.

Here is pTrel:

And here is d0:

The shape of the mistag distribution is clearly different than the W+light MC in both variables.  The mistag response needs to be changed.

Next I try to do the simultaneous fit to the pTrel and d0 distributions for the soft electron samples in both the TCE and CMUP/CMX samples.  Here is the TCE fit.

And here is the combined CMUP/CMX fit

We see an excess at large |d0| in both samples.

We think the excess in at high pTrel for soft muons in the high-pT muon triggered sample is now understood.  The effect comes from two sources:

1. A bug in the code that allowed muon near 20 GeV to be counted twice.
2. Our background templates did not take the Drell Yan contribution into account.

Below we have plots of the pTrel in the data, from the mistag prediction, and from the MC templates including DY.

CMUP

CMX

We see that the Drell Yan contribution has a long tail at high pTrel.  There is an easy way to remove this contribution, as can be seen in the stacked plot below.

First we notice that the MC underpredicts the total number of soft muon events.  We can also see that we should remove the mass region near the Z mass.  The DY events that go below the Z mass likely have a radaited photon.  We can remove those events by making selection on the EM fraction.  Finally, notice that the number of events in data increases below m=5 GeV with no corresponding increase in the MC prediction.  We believe these events may be due to b-bbar production.  We will likely have to cut this region away as well.

Even though we plan to remove these events, I went ahead and fit d0 & pTrel in the muons with the DY template added to see if any remaining excess at high pTrel was covered by the DY template.  The fit below is only for muon-triggered events, since that is where we first saw the excess.

As is seen in the post below, there is an excess of soft muons at high pTrel relative to what is expected from the SM MC.  Here I put some further plots examining this anomaly.

First we have the 2d pTrel vs. d0 plot to see if these high pTrel tracks also have high impact parameter.

They do not.  Next we look at run dependence.

No run dependence is observed.  The next plot compares the distribution of pTrel in postively charged soft muons to negatively charged soft muons.

Both distributions have a tail.  Finally we look at pTrel vs. dphi with respect to the high pT trigger muon.

The high pTrel tracks are going in the same direction or back-to-back with the trigger muon.

I have done a 2 dimensional fit to the pTrel and signed impact parameter distributions for soft muons.  The fitting function is a simple product of template pdfs obtained from the heavy flavor W+bb and W+cc MC for the bottom and charm, and W+jets for the light flavor.  The data selection here is standard W(met>25, mT>20, pT(lep)>20) + soft muon ID (soft muon likelihood < 3.5).  The fits are shown below for the electron and muon triggered W events separately.

Two interesting things to note:

1. The bottom and charm fractions are inconsistent between the different triggers.
2. The muon triggered sample has an excess of soft muons at high pTrel.  This needs further examinations – emTiming, pSum, event displays, etc.

Below I compare the pTrel distributions of soft muons from heavy flavor and light flavor MC to the distribution predicted by the muon mistag matrix on the inclusive W sample and the distribution obtained from the soft muon-tagged data.  All plots are normalized to unit area.  The comparison is done separately for each trigger type.

TCE

CMUP

CMX

All the shapes appear reasonable to me.  The mistag shape follows the shape of the light flavor MC quite well, as expected.