This document describes a method for predicting backgrounds to top-antitop quark events using b-tagging information. The method involves measuring b-tagging rates in gamma+jets events and applying those rates to other events to predict whether they would contain one or more b-tagged jets. The rates are measured as functions of muon momentum and position. Applying the rates to gamma+jets, jet, and lepton+jets data shows good agreement, validating the method. The method is then used to predict top-antitop and W+jets backgrounds in lepton+jets data and measure the top-antitop production cross section.
A Shore Introduction to Quantum Computer and the computation of ( Quantum Mechanics),
Nowadays we work on classical computer that work with bits which is either 0s or 1s, but Quantum Computer work with qubits which is either 0s or 1s or 0 and 1 in the same time.
MRS Dec 2010 Steel With Copper Precipitates Dierk Raabe Dierk Raabe
Copper nanoprecipitates in steel studied by atom probe tomography and ab initio based Monte Carlo simulation
Authors: O. Dmitrieva, P.-P. Choi, T. Hickel, N. Tillack,
D. Ponge, J. Neugebauer, D. Raabe
MRS Fall Meeting 2010
A Shore Introduction to Quantum Computer and the computation of ( Quantum Mechanics),
Nowadays we work on classical computer that work with bits which is either 0s or 1s, but Quantum Computer work with qubits which is either 0s or 1s or 0 and 1 in the same time.
MRS Dec 2010 Steel With Copper Precipitates Dierk Raabe Dierk Raabe
Copper nanoprecipitates in steel studied by atom probe tomography and ab initio based Monte Carlo simulation
Authors: O. Dmitrieva, P.-P. Choi, T. Hickel, N. Tillack,
D. Ponge, J. Neugebauer, D. Raabe
MRS Fall Meeting 2010
THE COORDINATE RATIOS AS A TOOL TO ANALYZE THE INTRUSION BASED ON BUŽEK-HILLE...IJNSA Journal
The intrusion based on Bužek-Hillery universal quantum copying machine (UQCM) is investigated. A major problem to the eavesdropper Eve is how to choose the intrusion parameters required by the copying machine in order to take out the maximum of information on the transmitted qubits while making her intrusion as discrete as possible. The present paper attempts to investigate the equatorial and isotropic cloning by means of coordinate ratios. The degree of intrusion is evaluated by means of the ratios of the receiver (Bob) coordinates and the eavesdropper (Eve) coordinates to the sender (Alice) coordinates in the Bloch sphere. The fidelity has been usually used as a criterion to analyze the intrusion. More especially, this fidelity can achieve the value 0.85 for equatorial qubits by using Bužek-Hillery 1→2 machine. Our goal is to study the behavior of these ratios as a function of the intrusion parameters. As has been found, the coordinate ratios of both the receiver and the eavesdropper achieve an optimal value higher than 2/3, in contrast to the isotropic cloning. This can favor the eavesdropping when using equatorial qubits. For isotropic cloning, the maximal intrusion is reached when the coordinate ratios are equal. The optimal values of the intrusion parameters are then evaluated.
P-Wave Onset Point Detection for Seismic Signal Using Bhattacharyya DistanceCSCJournals
In seismology Primary p-wave arrival identification is a fundamental problem for the geologist worldwide. Several numbers of algorithms that deal with p-wave onset detection and identification have already been proposed. Accurate p- wave picking is required for earthquake early warning system and determination of epicenter location etc. In this paper we have proposed a novel algorithm for p-wave detection using Bhattacharyya distance for seismic signals. In our study we have taken 50 numbers of real seismic signals (generated by earthquake) recorded by K-NET (Kyoshin network), Japan. Our results show maximum standard deviation of 1.76 sample from true picks which gives better accuracy with respect to ratio test method.
1PHY 4822L (Advanced Laboratory) Analysis of a bu.docxmadlynplamondon
1
PHY 4822L (Advanced Laboratory):
Analysis of a bubble chamber picture
Introduction
In this experiment you will study a reaction between “elementary particles” by analyzing their
tracks in a bubble chamber. Such particles are everywhere around us [1,2]. Apart from the standard
matter particles proton, neutron and electron, hundreds of other particles have been found [3,4],
produced in cosmic ray interactions in the atmosphere or by accelerators. Hundreds of charged
particles traverse our bodies per second, and some will damage our DNA, one of the reasons for the
necessity of a sophisticated DNA repair mechanism in the cell.
2
Figure 1: Photograph of the interaction between a high-energy π--meson from the Berkeley
Bevatron accelerator and a proton in a liquid hydrogen bubble chamber, which produces two neutral
short-lived particles Λ0 and K0 which decay into charged particles a bit further.
Figure 2: illustration of the interaction, and identification of bubble trails and variables to be
measured in the photograph in Figures 3 and 4.
The data for this experiment is in the form of a bubble chamber photograph which shows bubble
tracks made by elementary particles as they traverse liquid hydrogen. In the experiment under
study, a beam of low-energy negative pions (π- beam) hits a hydrogen target in a bubble chamber.
A bubble chamber [5] is essentially a container with a liquid kept just below its boiling point (T=20
K for hydrogen). A piston allows expanding the inside volume, thus lowering the pressure inside
the bubblechamber. When the beam particles enter the detector a piston slightly decompresses the
liquid so it becomes "super-critical'' and starts boiling, and bubbles form, first at the ionization
trails left by the charged particles traversing the liquid.
The reaction shown in Figure 1 shows the production of a pair of neutral particles (that do not leave
a ionized trail in their wake), which after a short while decay into pairs of charged particles:
π - + p → Λo + Ko,
3
where the neutral particles Λo and Ko decay as follows:
Λo → p + π-, Ko → π+ + π-.
In this experiment, we assume the masses of the proton (mp = 938.3 MeV/c2) and the pions (mπ+ =
mπ- = 139.4 MeV/c2) to be known precisely, and we will determine the masses of the Λ0 and the K0,
also in these mass energy units.
Momentum measurement
In order to “reconstruct” the interaction completely, one uses the conservation laws of (relativistic)
momentum and energy, plus the knowledge of the initial pion beam parameters (mass and
momentum). In order to measure momenta of the produced charged particles, the bubble chamber is
located inside a magnet that bends the charged particles in helical paths. The 1.5 T magnetic field is
directed up out of the photograph. The momentum p of each particle is directly proportional to the
radius of curvature R, which in turn can be calculated fro.
1PHY 4822L (Advanced Laboratory) Analysis of a bu.docxpoulterbarbara
1
PHY 4822L (Advanced Laboratory):
Analysis of a bubble chamber picture
Introduction
In this experiment you will study a reaction between “elementary particles” by analyzing their
tracks in a bubble chamber. Such particles are everywhere around us [1,2]. Apart from the standard
matter particles proton, neutron and electron, hundreds of other particles have been found [3,4],
produced in cosmic ray interactions in the atmosphere or by accelerators. Hundreds of charged
particles traverse our bodies per second, and some will damage our DNA, one of the reasons for the
necessity of a sophisticated DNA repair mechanism in the cell.
2
Figure 1: Photograph of the interaction between a high-energy π--meson from the Berkeley
Bevatron accelerator and a proton in a liquid hydrogen bubble chamber, which produces two neutral
short-lived particles Λ0 and K0 which decay into charged particles a bit further.
Figure 2: illustration of the interaction, and identification of bubble trails and variables to be
measured in the photograph in Figures 3 and 4.
The data for this experiment is in the form of a bubble chamber photograph which shows bubble
tracks made by elementary particles as they traverse liquid hydrogen. In the experiment under
study, a beam of low-energy negative pions (π- beam) hits a hydrogen target in a bubble chamber.
A bubble chamber [5] is essentially a container with a liquid kept just below its boiling point (T=20
K for hydrogen). A piston allows expanding the inside volume, thus lowering the pressure inside
the bubblechamber. When the beam particles enter the detector a piston slightly decompresses the
liquid so it becomes "super-critical'' and starts boiling, and bubbles form, first at the ionization
trails left by the charged particles traversing the liquid.
The reaction shown in Figure 1 shows the production of a pair of neutral particles (that do not leave
a ionized trail in their wake), which after a short while decay into pairs of charged particles:
π - + p → Λo + Ko,
3
where the neutral particles Λo and Ko decay as follows:
Λo → p + π-, Ko → π+ + π-.
In this experiment, we assume the masses of the proton (mp = 938.3 MeV/c2) and the pions (mπ+ =
mπ- = 139.4 MeV/c2) to be known precisely, and we will determine the masses of the Λ0 and the K0,
also in these mass energy units.
Momentum measurement
In order to “reconstruct” the interaction completely, one uses the conservation laws of (relativistic)
momentum and energy, plus the knowledge of the initial pion beam parameters (mass and
momentum). In order to measure momenta of the produced charged particles, the bubble chamber is
located inside a magnet that bends the charged particles in helical paths. The 1.5 T magnetic field is
directed up out of the photograph. The momentum p of each particle is directly proportional to the
radius of curvature R, which in turn can be calculated fro.
Investigation of repeated blasts at Aitik mine using waveform cross correlationIvan Kitov
We present results of signal detection from repeated events at the Aitik and Kiruna mines in Sweden as based on waveform cross correlation. Several advanced methods based on tensor Singular Value Decomposition is applied to waveforms measured at seismic array ARCES, which consists of three-component sensors.
Investigation of repeated events at Jordan phosphate mine with waveform cross...Ivan Kitov
More than 1500 events were measured at 3 seismic stations. Their signals are processed using waveform cross correlation and Principal Component Analysis. The best waveforms and eigenvectors are used for detection.
Reliability Evaluation of Low-voltage Switchgear Based on Maximum Entropy Pri...TELKOMNIKA JOURNAL
In this paper, based on the definition of two-parameter joint entropy and the maximum entropy principle, a method was proposed to determine the prior distribution by using the maximum entropy method in the reliability evaluation of low-voltage switchgear. The maximum entropy method takes kinds of priori information as different constraints. The optimal prior distribution was selected by maximizing entropy under these constraints, which not only contains the known prior information but also tries to avoid the introduction of other assumption information. Based on non-parametric bootstrap method, the hyper-parameters of prior distribution is obtained by two-order moment of prior information. Finally, with the bootstrap method, the prior distribution robustness and the posterior robustness were analyzed, and the posterior mean time between failures for the low-voltage switchgear was estimated.
THE COORDINATE RATIOS AS A TOOL TO ANALYZE THE INTRUSION BASED ON BUŽEK-HILLE...IJNSA Journal
The intrusion based on Bužek-Hillery universal quantum copying machine (UQCM) is investigated. A major problem to the eavesdropper Eve is how to choose the intrusion parameters required by the copying machine in order to take out the maximum of information on the transmitted qubits while making her intrusion as discrete as possible. The present paper attempts to investigate the equatorial and isotropic cloning by means of coordinate ratios. The degree of intrusion is evaluated by means of the ratios of the receiver (Bob) coordinates and the eavesdropper (Eve) coordinates to the sender (Alice) coordinates in the Bloch sphere. The fidelity has been usually used as a criterion to analyze the intrusion. More especially, this fidelity can achieve the value 0.85 for equatorial qubits by using Bužek-Hillery 1→2 machine. Our goal is to study the behavior of these ratios as a function of the intrusion parameters. As has been found, the coordinate ratios of both the receiver and the eavesdropper achieve an optimal value higher than 2/3, in contrast to the isotropic cloning. This can favor the eavesdropping when using equatorial qubits. For isotropic cloning, the maximal intrusion is reached when the coordinate ratios are equal. The optimal values of the intrusion parameters are then evaluated.
P-Wave Onset Point Detection for Seismic Signal Using Bhattacharyya DistanceCSCJournals
In seismology Primary p-wave arrival identification is a fundamental problem for the geologist worldwide. Several numbers of algorithms that deal with p-wave onset detection and identification have already been proposed. Accurate p- wave picking is required for earthquake early warning system and determination of epicenter location etc. In this paper we have proposed a novel algorithm for p-wave detection using Bhattacharyya distance for seismic signals. In our study we have taken 50 numbers of real seismic signals (generated by earthquake) recorded by K-NET (Kyoshin network), Japan. Our results show maximum standard deviation of 1.76 sample from true picks which gives better accuracy with respect to ratio test method.
1PHY 4822L (Advanced Laboratory) Analysis of a bu.docxmadlynplamondon
1
PHY 4822L (Advanced Laboratory):
Analysis of a bubble chamber picture
Introduction
In this experiment you will study a reaction between “elementary particles” by analyzing their
tracks in a bubble chamber. Such particles are everywhere around us [1,2]. Apart from the standard
matter particles proton, neutron and electron, hundreds of other particles have been found [3,4],
produced in cosmic ray interactions in the atmosphere or by accelerators. Hundreds of charged
particles traverse our bodies per second, and some will damage our DNA, one of the reasons for the
necessity of a sophisticated DNA repair mechanism in the cell.
2
Figure 1: Photograph of the interaction between a high-energy π--meson from the Berkeley
Bevatron accelerator and a proton in a liquid hydrogen bubble chamber, which produces two neutral
short-lived particles Λ0 and K0 which decay into charged particles a bit further.
Figure 2: illustration of the interaction, and identification of bubble trails and variables to be
measured in the photograph in Figures 3 and 4.
The data for this experiment is in the form of a bubble chamber photograph which shows bubble
tracks made by elementary particles as they traverse liquid hydrogen. In the experiment under
study, a beam of low-energy negative pions (π- beam) hits a hydrogen target in a bubble chamber.
A bubble chamber [5] is essentially a container with a liquid kept just below its boiling point (T=20
K for hydrogen). A piston allows expanding the inside volume, thus lowering the pressure inside
the bubblechamber. When the beam particles enter the detector a piston slightly decompresses the
liquid so it becomes "super-critical'' and starts boiling, and bubbles form, first at the ionization
trails left by the charged particles traversing the liquid.
The reaction shown in Figure 1 shows the production of a pair of neutral particles (that do not leave
a ionized trail in their wake), which after a short while decay into pairs of charged particles:
π - + p → Λo + Ko,
3
where the neutral particles Λo and Ko decay as follows:
Λo → p + π-, Ko → π+ + π-.
In this experiment, we assume the masses of the proton (mp = 938.3 MeV/c2) and the pions (mπ+ =
mπ- = 139.4 MeV/c2) to be known precisely, and we will determine the masses of the Λ0 and the K0,
also in these mass energy units.
Momentum measurement
In order to “reconstruct” the interaction completely, one uses the conservation laws of (relativistic)
momentum and energy, plus the knowledge of the initial pion beam parameters (mass and
momentum). In order to measure momenta of the produced charged particles, the bubble chamber is
located inside a magnet that bends the charged particles in helical paths. The 1.5 T magnetic field is
directed up out of the photograph. The momentum p of each particle is directly proportional to the
radius of curvature R, which in turn can be calculated fro.
1PHY 4822L (Advanced Laboratory) Analysis of a bu.docxpoulterbarbara
1
PHY 4822L (Advanced Laboratory):
Analysis of a bubble chamber picture
Introduction
In this experiment you will study a reaction between “elementary particles” by analyzing their
tracks in a bubble chamber. Such particles are everywhere around us [1,2]. Apart from the standard
matter particles proton, neutron and electron, hundreds of other particles have been found [3,4],
produced in cosmic ray interactions in the atmosphere or by accelerators. Hundreds of charged
particles traverse our bodies per second, and some will damage our DNA, one of the reasons for the
necessity of a sophisticated DNA repair mechanism in the cell.
2
Figure 1: Photograph of the interaction between a high-energy π--meson from the Berkeley
Bevatron accelerator and a proton in a liquid hydrogen bubble chamber, which produces two neutral
short-lived particles Λ0 and K0 which decay into charged particles a bit further.
Figure 2: illustration of the interaction, and identification of bubble trails and variables to be
measured in the photograph in Figures 3 and 4.
The data for this experiment is in the form of a bubble chamber photograph which shows bubble
tracks made by elementary particles as they traverse liquid hydrogen. In the experiment under
study, a beam of low-energy negative pions (π- beam) hits a hydrogen target in a bubble chamber.
A bubble chamber [5] is essentially a container with a liquid kept just below its boiling point (T=20
K for hydrogen). A piston allows expanding the inside volume, thus lowering the pressure inside
the bubblechamber. When the beam particles enter the detector a piston slightly decompresses the
liquid so it becomes "super-critical'' and starts boiling, and bubbles form, first at the ionization
trails left by the charged particles traversing the liquid.
The reaction shown in Figure 1 shows the production of a pair of neutral particles (that do not leave
a ionized trail in their wake), which after a short while decay into pairs of charged particles:
π - + p → Λo + Ko,
3
where the neutral particles Λo and Ko decay as follows:
Λo → p + π-, Ko → π+ + π-.
In this experiment, we assume the masses of the proton (mp = 938.3 MeV/c2) and the pions (mπ+ =
mπ- = 139.4 MeV/c2) to be known precisely, and we will determine the masses of the Λ0 and the K0,
also in these mass energy units.
Momentum measurement
In order to “reconstruct” the interaction completely, one uses the conservation laws of (relativistic)
momentum and energy, plus the knowledge of the initial pion beam parameters (mass and
momentum). In order to measure momenta of the produced charged particles, the bubble chamber is
located inside a magnet that bends the charged particles in helical paths. The 1.5 T magnetic field is
directed up out of the photograph. The momentum p of each particle is directly proportional to the
radius of curvature R, which in turn can be calculated fro.
Investigation of repeated blasts at Aitik mine using waveform cross correlationIvan Kitov
We present results of signal detection from repeated events at the Aitik and Kiruna mines in Sweden as based on waveform cross correlation. Several advanced methods based on tensor Singular Value Decomposition is applied to waveforms measured at seismic array ARCES, which consists of three-component sensors.
Investigation of repeated events at Jordan phosphate mine with waveform cross...Ivan Kitov
More than 1500 events were measured at 3 seismic stations. Their signals are processed using waveform cross correlation and Principal Component Analysis. The best waveforms and eigenvectors are used for detection.
Reliability Evaluation of Low-voltage Switchgear Based on Maximum Entropy Pri...TELKOMNIKA JOURNAL
In this paper, based on the definition of two-parameter joint entropy and the maximum entropy principle, a method was proposed to determine the prior distribution by using the maximum entropy method in the reliability evaluation of low-voltage switchgear. The maximum entropy method takes kinds of priori information as different constraints. The optimal prior distribution was selected by maximizing entropy under these constraints, which not only contains the known prior information but also tries to avoid the introduction of other assumption information. Based on non-parametric bootstrap method, the hyper-parameters of prior distribution is obtained by two-order moment of prior information. Finally, with the bootstrap method, the prior distribution robustness and the posterior robustness were analyzed, and the posterior mean time between failures for the low-voltage switchgear was estimated.
1. B TAGGING
A b quark has a chance of decaying into a low energy (soft) lep-
ton and an up or charm quark. B tagging, the process of identifying a
jet as a b jet, is done via algorithms that pair quarks with soft muons
that are close enough to the jet, appear to originate from a point in
space near the jet, and have energy and momentum such that it is
likely that said soft muon came from a b quark in that jet.
EXPERIMENTAL METHOD AND RESULTS
We hypothesize that γ+jets events (similar to W+jets, but pro-
ducing a photon that does not decay instead of a decaying W boson)
produce the same mixture of jet flavors as W+jets events. Since the
γ+jets is large and relatively pure (there is no relatively pure W+jets
data), we measured the probability, referred to as the tag rate, in
γ+jets data that a given track that is close to jet will be a soft muon
that causes said jet to be tagged. We create the tag rate as a function
of pT, the muon’s momentum in the direction orthogonal to the
beamline, and |ηdet|, a value representing the muon’s position in the
detectorb
.
Predicting W+jets background to top-antitop events in the Large Hadron Collider
Ken Bloom1
, Aaron Dominguez1
, Maxwell Gregoire1
, Jason Keller1
, Tuula Maki2
, Helena Malbouisson1
, Jeff Temple3
,
Don Teo4
, and Peter Wittich4
1 University of Nebraska-Lincoln, United States; 2 CERN; 3 University of Maryland, United States; 4 Cornell University, United States
INTRODUCTION
The Large Hadron Collider (LHC) at CERN, Switzerland, is cur-
rently colliding beams of particles with record-high center-of-mass
energy of 7 TeV, much higher than the energy of the collisions at the
Tevatron in Fermilab, IL, which peak at 1.96 TeV[1][2]
. At higher ener-
gies, we are able to observe more particles of higher massa
. tt̅ events,
events in which a top quark and anti-top quark are produced, are es-
pecially important because they are plentiful, have an accurately-
predicted production rate, and involve the production of many differ-
ent particles. We choose to analyze tt̅ events in order to better under-
stand the detector. One of the first steps to analyzing tt̅ events is un-
derstanding the background, or non tt̅ events that appear to be tt̅
events.
THE COMPACT MUON SOLENOID
The detector we work with is the Compact Muon Solenoid
(CMS), a general purpose detector optimized for muon detection.
CMS uses a silicon tracker, muon detectors, and electromagnetic and
hadronic calorimeters to detect and identify particles. Muons are de-
tected by the tracker and muon detectors and leave few traces in the
calorimeters. Quarks and gluons appear as jets, collimated streams of
many types of particles (mostly hadrons), in the calorimeters and the
trackers.
TT̅ EVENTS AND W+JETS EVENTS
Figure 2 diagrams a typical W+jets event and tt̅ event and
shows how those events appear to the detector. In each event the de-
tector detects a muon, a neutrino, and four jets; the only difference is
that we expect two b jets in tt̅ events, while the jets in W+jets events
are much less likely to include two b jets. Since non-b jets are often
mistaken for b jets, and since the jets in W+jets events sometimes are
b jets, we expect to have W+jets events sometimes look like as tt̅
events in the detector. W+jets events comprise the largest portion of
the tt̅ background.
REFERENCES
[1] “LHC Machine Outreach” http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/
(retrieved March 1, 2011)
[2] “LHC Beam” http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/beam.htm
(retrieved March 1, 2011)
[3] “Overview of CMS Physics Goals and Detector” https://twiki.cern.ch/twiki/bin/view/
CMSPublic/WorkBookCMSExperiment (retrieved March 1, 2011)
Fig. 1[3]
: Description of how different particles are detected in the CMS detector.
The tag rate is roughly-constant for all pT except high pT, in which case
the tag rate decreases drastically. The tag rate increases subtly as
|ηdet| with fluctuations at 1.4 and 2.2.
To apply the tag rate to a data sample, we scale a parameter of
our choice in each event by the factor 1 - ∏i
all tracks
[ 1 - Pi(pT , ηdet) ],
which represents the probability that the event will contain at least
one b tagd
. For our analysis, we choose jet multiplicity per event as
our parameter because we expect a dependence of tt̅ and tt̅ back-
ground levels on jet multiplicity.
First, we apply the tag rate to the γ+jets sample from which it
was created to verify the accuracy of our method. We compare the
scaled jet multiplicity to the jet multiplicity for only events containing
at least one b tag.
The results of this closure test show that our method can accurately
predict the γ+jets contribution to a given data set.
Next, we applied the tag rate to a sample of jet data.
The high level of agreement of this application verifies our hypothe-
sis; Our tag rate produced from γ+jets data is capable of predicting
other jet backgrounds, particularly W+jets background.
Finally, we use the tag rate to predict the tt̅ and W+jets contri-
butions to the l+jets data (events containing at least one high-energy
lepton and any number of jets). We use the following iterative
method:
Fig. 4: The tag rate as a function of pT (top) and ηdet (bottom)c
.
FOOTNOTES
a. The equation E=mc2
illustrates how higher energies are likely to produce higher numbers of
more-massive particles.
b.ηdet = -ln( tan( θ / 2 ) ), where θ is the angle between the beamline and the vector from the cen-
ter of the detector to the point at which the particle entered the detector.
c. The tag rate is actually a multivariable function of pT and ηdet, as opposed to the two separate
single-variable functions of each parameter shown in figure 3. However, the displayed plots
provide a better visual representation of the tag rate.
d.The scaling factor 1 - ∏i
all tracks
[ 1 - Pi(pT , ηdet) ] is different for each event since the number of
tracks and their respective pT and ηdet are different for each event.
Since events with low jet multiplicity are very unlikely to be tt̅ events,
our results show that our method correctly estimates the non-tt̅ con-
tributions to the data. This agreement implies that we can also esti-
mate the non-tt̅ contributions to events with higher jet multiplicity
which we do expect to have significant tt̅ contribution.
CONCLUSIONS
We can correct for the geometric limitations of the detector,
the limited efficiency of kinematic requirements, and the fact that
some tt̅ events contain b jets that do not have tagging muons to ob-
tain an estimate of the number of tt̅ events. We can divide this num-
ber by the integrated luminosity, 36 pb-1
, to obtain the tt̅ cross sec-
tion.
σtt̅ = 150 ± 9 (stat.) ± 17 (syst.) ± 6 (lumi.) pb
This matches the theoretical prediction of 164-13
+10
pb within uncer-
tainty. The greatest part of our uncertainty is derived from how accu-
rately we are able to describe the tt̅ background using the tag rate.
Fig. 2: A diagram of a tt̅ event and W+jets event in the CMS detector. Objects be-
low the “detector” line represent particles that reach the detector. Quarks mani-
fest themselves in the detector as jets.
Fig. 6: Application of the tag rate to the jet data.
——— jet multiplicity scaled by 1 - ∏i
all tracks
[ 1 - Pi(pT , ηdet) ]
● jet multiplicity for events with at least one b tag
Fig. 5: Application of the tag rate to the γ+jets data from which it was created.
——— jet multiplicity scaled by 1 - ∏i
all tracks
[ 1 - Pi(pT , ηdet) ]
● jet multiplicity for events with at least one b tag
Fig. 7: Flowchart depicting iterative method that predicts the tt̅ and W+jets con-
tributions to the l+jets data.
l+jets data
1. apply tag rate
prediction of
amount of tagged
W+jets data
2. subtract from
actual amount of
tagged W+jets data
amount of tt̅ in
tagged W+jets data
4. use as
correction
factor on
3. impliesamount of tt̅
in l+jets data
START
First iteration: assume all
l+jets data is W+jets data.
Repeat until
converges
Fig. 8: The composition of l+jets data.
● total l+jets data
primary muon,
pT: 45.1 GeV/c
b-tagged jet,
pT: 38.4 GeV/c
soft muon,
pT: 5.5 GeV/c
Fig. 3: Diagram of an event containing a high-energy muon, a b-tagged jet, and a
tagging soft muon.
cones = jets; lines = muons; bars = energy depositions in the calorimeters
ACKNOWLEDGEMENTS
UCARE and the National Science Foundation, for funding.
The LHC accelerator physicists, for the excellent performance of the machine.