VHF working meeting, 4 Oct Measurement of associated charm production in W final states at  s=7TeV J. Alcaraz, I. Josa, J. Santaolalla (CIEMAT, Madrid) VHF working meeting Measurement of associated charm production in W final states at  s=7TeV J. Alcaraz, I. Josa, J. Santaolalla (CIEMAT, Madrid) VHF working meeting

VHF working meeting, 4 Oct What we measure  In “W+c”, the W production proceeds predominantly via “gluon + s-quark”: g + s  cc + s  c + W  ”. Direct access to s quark PDF Our signal 1

VHF working meeting, 4 Oct Valence quark contribution for W - : g + d  cc + d  W - + c. The anti-strange contribution of this process is even more suppressed since d-bar is not a valence quark. d d What we measure Other W+c contributions 2 Cabibbo suppresed d is valence quark

VHF working meeting, 4 Oct Gluon splitting of the type: u + d  W + + g  W + + cc bar. Two c quarks in the final state. It will be part of our signal What we measure Other W+c contributions 2

VHF working meeting, 4 Oct We use 2.2 fb -1 of LHC 2011 data runA and runB, in the next step we will use 2 fb -1 of runA data W  decay channel (no plans of using e data) Data: Selection of W bosons: follow the standard VBTF criteria to select a pure W sample Enhancement of c jets: b-tagging discriminator Data sample Our data 3 Will work since W+b sample is small enough

VHF working meeting, 4 Oct We use MADGRAPH as our reference (with 2010 data we used POWHEG instead) List of MC samples used in the analysis: MC samples Our MC PileUp conditions New samples

VHF working meeting, 4 Oct How we measure it W  inclusive selection (same as in 2010)  Jet Seleccion, same as in 2010 except  SV mass lower than 2 GeV  Leptonic W jet systems’s mass lower than 300 GeV  Less than 2 jets above 40 GeV to reduce top backgrounds (less than 3 jets in 2010 analysis) Selection 1

VHF working meeting, 4 Oct How we measure it W  inclusive selection  Jet Seleccion Selection 1 Dominant backgrounds Largely Reduced with New cuts

VHF working meeting, 4 Oct How we measure it W  inclusive selection  Jet Seleccion Selection 1 Dominant backgrounds Largely Reduced with New cuts We finally plot the b- discriminator of the most significant jet

VHF working meeting, 4 Oct  Simple Secondary Vertex High Efficiency discriminator  D SSVHE = log(1+decayLengthSignificance)  SENSITIVITY TO SIGNAL AND BACKGROUNDS W+W+W+W+ W-W-W-W- How we measure it c-tag discriminator 2 Same procedure as in 2010

VHF working meeting, 4 Oct  Negative vertices help to constrain the light-quark contribution below the charm signal peak  Cross checks with TCHE discriminant (see later) W+W+W+W+ W-W-W-W- How we measure it Fit the D SSVHE distribution 3

VHF working meeting, 4 Oct Results The fit 1  Fit to 3 components: light quarks, signal, top  Shape taken from MC  Different shape of contributions allows to have a good discriminant power. Ttbar and s-top have similar shape 'harder' than W+charm

VHF working meeting, 4 Oct W+W+W+W+ W-W-W-W-Results Output of the fit 2

VHF working meeting, 4 Oct Results Ratios 2  The efficiency includes the tagging efficiency, but also implicit corrections that bring the ratio to the MCFM expected definition at the parton level (acceptance effects, hadronization effects)

VHF working meeting, 4 Oct Systematics for charm charge ratio Similar procedure to 2010 analysis In progress

VHF working meeting, 4 Oct Systematics for charm ratio

VHF working meeting, 4 Oct Other plots W boson transverse mass

VHF working meeting, 4 Oct Other plots Pt of jet # jets Better agreement than in 2010 analysis (POWHEG)

VHF working meeting, 4 Oct Other plots Jet charged multiplicity

VHF working meeting, 4 Oct Other plots Jet eta

VHF working meeting, 4 Oct Other plots # of tracks per vertex

VHF working meeting, 4 Oct Other discriminants TCHE discriminator

VHF working meeting, 4 Oct Other discriminants SV high purity Largely reduces light contribution. However, it also reduces signal contribution. Light contribution is in principle under control.

VHF working meeting, 4 Oct To do list and important remarks for 2011 data The use of MADGRAPH instead of POWHEG allows us to set a more restrictive cut in the #jets We reduce top rel. backgrounds (not dominant now) WplusJets MC sample seems to be wrongly normalized. A 10% increase in MC normalization was necessary to reach better agreement. MC statistics start to be insufficient (same order as data). W+1jet, W+2 jet… instead of W+jets We are planning to change the way some systematics are assigned (the most critical ones) In this presentation, 2.2 fb-1 of data were used. In the future we plan to restrict it to the 2 fb-1 of runA We plan to use the muon charge information to better compute the efficiency.

VHF working meeting, 4 Oct We took a first look to 2011 data. Preliminary result were shown. Everything worked out-of-the-box (except MC normalization of signal sample) Big amount of data allow us to: envisage new methods to improve our confidence on the analysis and to decrease the systematic uncertainties. enter a systematic dominated era. An analysis note (AN ) is being redacted. CONCLUSIONS