Yep, so please go ahead.
Okay, so um I'm going to um talk about new um
Top quark properties measurements from our ATLAS and CMS um experiments.
um so, as you have heard several times the top quark is the most massive um elementary particle
known to date. So it has a very short lifetime which is um shorter than the
hadronization timescale. So no hadronic bound states can form so it's quark
properties are accessible. Moreover, um its lifetime is shorter than the spin
decorrelation time scale so their top quark spins stay correlated and can be measurable.
um you can find all public results about top quark from ATLAS and CMS in these links
here I will focus on recent measurements um from ATLAS and CMS.
um and I'll cover top quark mass and width, Yukawa couplings, CKM matrix elements,
asymmetries, spin correlations and um W polarization.
um top Quark mass um can be extracted from its decay. So here um is a list of um
measurements from CMS and ATLAS up to may 2019. For such measurements um and some
of them are not included yet, some new measurements aren't included yet, and I'll
talk about the ATLAS lepton plus jets from soft muon tags measurement later.
um you can see in the blue highlighted parts the combination from Atlas combinations from
Atlas and CMS, both have reached the precision of five hundred MeV which corresponds to
zero point twenty eight per cent.
And these measurements are limited by jet energy scale calibration, b tagging
and modeling uncertainties. and there're many individual measurements with less than one GeV
uncertainty now, and at these levels of uncertainties the interpretation of top
mass measurements is um complicated due to non perturbative effects which can be up
to um even one GeV. So it's important to measure top mass in well defined mass
schemes and with independent methods.
um one of the different methods is to extract top masses from production observables
using total and differential ttbar cross sections.
So here is a um summary of of these measurements, and the the two recent one ones
from Atlas and CMS and they're also the most um precise ones. I will um talk about next
slide. In general, these measurements are dominated by um ttr ttbar threshold production
and there the uncertainties due to PDFs and
higher order corrections are more important than other uncertainties.
This measurement is from CMS using triple differential normalized cross sections
using number of jets,um tt bar invariant mass and rapidity off the tt bar system.
Along with that, HERA DIS data is also used to simultaneous extract PDF alpha s and
top mass at nlo.
um so, you can see the distribution of um TT bar rapidity, in bins of number of jets
and um invariant mass. So, you can see that the region the threshold region, um about two top
mass is the most sensitive region with you can see the different top mass assumptions
here.
um but also that's not the only sensitive region. The resulting mass
top poll mass is hundred seventy point five GeV with a precision of zero point five percent. this is dominated
by by bought experiments, um modeling uncertainties. And you can also see the
alpha s value extracted from this triple differential measurement. And the this plot
shows the significant impact on the gluon PDF at at high x values.
um ATLAS made a measurement of top mass both top pole mass and MS bar mass using
TT bar plus one jet events in lepton plus jets channel. For this the the rho s variable
is used. So, this is the inverse of the TT bar plus one jet invariant mass normalized
to a reference mass scale. And you can see the distribution of the rho s variable and the
different poll mass assumptions and compared to data
and the the extracted values are for MS bar masses hundred seventy two point 9 GeV and pole
masses hundred seventy one point one
GeV.
So when the MS bar mass is translated to the pole mass using this formula here, we see
that the agreement is is very well for the two measurements. And these measurements
are dominated by scale PDF, parton shower, color connection, jet en and jet energy scale
uncertainties
um while the MS bar mass has somewhat larger theory uncertainty and this is due to the larger dependence
on scales at the at the threshold
CMS made the first experimental investigation of the running of the top quark
mass, which is extracted at one loop precision as a function of the invariant mass
of the TT Bar system by comparing to NLO calculations
at the parton level and the measurement is done in the e mu channel. So, here you
can see the TT bar invariant mass with different
running mass predictions compared to data. And here this is the result of the of the
measurements. So the points are the result of the nlo extraction. And this is the
reference scale at four hundred sixty seven GeV, this is evolved using the renormalization group equations
and you can see the agreement of data with the predictions of the renormalization group
equations.
um here you can see the the blue points shows the NLO extraction from inclusive TT Bar cross
section measurement. And now this measurement is this result is evolved
again using the renormalization group equations and then compared to the extractions
in this analysis and you can see there's a very good agreement
also the no running scenario is excluded at the ninety five percent confidence level.
In this measurement the precision is limited by integrated luminosity lepton id
jet energy scale and resolution
and signal modeling.
So, to improve this measurement will need the NLO calculations in the MS bar
scheme
Top quark mass is also measured from boosted top jet mass by CMS in the lepton plus jets
channel. for this xcone algorithm is used to reconstruct the jet. So, you can see the
two large radius xcone jets here from from the TT bar system and here you can see the
hadronic leg and three there are three subjects which are again reconstructed using the xcone
subjects and these subjects are used to reconstruct the top jet mass that the
distribution can see here with different top mass assumptions and and the data and
using this the
at the particle level, the top mass is extracted to be hundred seventy two point six, the
precision of 1.4 percent. Here the experimental uncertainties are jet energy
scale resolution and xcone jet energy correction. for modeling final state radiation color
reconnection, underlying event tune, and top mass value. The average energy scale of measurement is
around four hundred eighty GeV which is significant larger than the scale in other top mass measurements. So
this gives us an independent check at higher scales. So this measurement
is is helping
to understand the ambiguities between Monte Carlo and pole masses, and also eventually aim
for analytical techniques determination in this boosted regime in the soft-collinear effective theory
Top quark mass is also measured using soft muon tags, by by the ATLAS experiment. So
here we have the soft muon from the B hadron and the muon from the W from the top quark decay is
used to reconstruct an l mu invariant mass and we can see the how how the distribution
changes for mlb for different top mass values. So the the lepton plus jets channel
is used with the requirement of two b tagged jets, one with displaced vertex and one with
the soft muon tag and simultaneous template fit to mlb distributions, both
for same sign opposite sign samples have been made to
extract the result.
Um to to in in increase the precision of the measurement, the fragmentation function
pythia eight is improved using a new fit to LEP data
and also b and c hadron decay branching ratios are ad adjusted to match of the
to match the previous measurements.
and here you can see the post fit distribution for the m l nu
compared to to Monte Carlo
and the result is hundred seventy four point fourty eight GeV with a precision of zero point forty five percent.
So here you can see this is sensitive to different modeling effects. So this this will
also be useful for combinations as well.
Top quark width is also measured by the ATLAS experiment
directly using a profile likelihood template fit to m l b distribution in the dilepton
channel and this measurement
uses full run two data. you can see the different predictions for mlb um from
different top width assumptions. Here you can see the post fit distribution, in the e mu
channel and the log likelihood minimization for the top width.
So, the measurements are compared to NLO predictions and the agreement is is
very good and dominant uncertainties of the measurement is jet reconstruction, signal
and background modeling, Monte Carlo statistics, flavor and flavor tagging.
As you heard in the in the first talk of this session Yukawa coupling is also
measured by CMS utilizing the weak corrections from
scalar bosons that modify um differential distributions. If we have
different Yukawa couplings which are larger than one. for the measurement, this YT variable
is used which is the
Yukawa coupling strength normalized to the Standard Model Yukawa coupling strength
and the the weak corrections as a function of MTT bar and delta YTT bar for different
Yukawa parameter values are calculated and they're applied to all TT bar samples so that
their kinematics remain depended on YT to be able to extract YT.
Um measurement is done in dilepton channel, requiring to opposite sign leptons and
two b jets. Um instead of um reconstructing fully MTT bar and Delta YTT bar a partial
reconstruction is done. And this is found to be more sensitive in the end. And here are
the two variables used mbl and delta y bl. And here's the distribution showing m b l um
as a function um in different bins of delta y
b l, as well.
And this is the post fit distribution. And here you can see the minimization of the log
likelihood and the measurement is dominated by electroweak correction parton
shower and matrix element scales and jet energy scale uncertainties. Measurement uses full run two
data and the resulting YT value is one point sixteen with these uncertainties and the ninety five percent
confidence limit for the upper limit is one point sixty two. This could be compared to the other
CMS result that's exclusively dependent on the top Yukawa coupling, which is from top quark
production and there the limit is at ninety five percent confidence which is at one point seven
In fact the best
measurement of this parameter comes from CMS Higgs combination, but it's a model
dependent result.
and um CMS also
measured the CKM matrix elements from single top quark t channel using processes
directly sensitive to V tb V td V ts matrix elements in production and decay. here are two
example diagrams. So, in this one the V tb appears both in production and decay. here
here it appears V tb appears in production and V tq appears in decay. the yields of
different signals are extracted through a simultaneous fit to data in different event
categories, there are two jet one tag, three jet one tag, three jet two tag and
using multivariate discriminators such as the example here
discriminating for example, this diagram from TT bar and the W plus jets
backgrounds. And CKM matrix elements from signal strengths calculated
from the cross section times branching ratios.
And here are the results so a signal strength from the
fit. And the constraints on the CKM matrix elements assuming CKM unitarity of the Standard
model or assuming additional quark families, the extracted values for V TB
and summed squares of these two matrix elements are here. And most interesting one is the is
the one
where we keep everything unconstrained and here V tb is zero point nine eight eight. And some squares are
zero point zero six and top width normalized to the standard model one is close to one. And the
measurement is dominated by modeling uncertainties. And these are in fact the
first direct model independent measurements of the CKM matrix elements for the third generation
quarks, and they are the best determinations of these um parameters.
um CMS made the first forward backward asymmetry
measurement at the LHC for TT bar. So the asymmetry arises due to the NLO
interference times between q q bar diagrams and this eventually leads to
slightly positive asymmetry. For the measurement, three variables are used cos
theta star, MTT bar, and x f.
And
for cos theta star, it's defined in the TT Bar rest frame. This is analogous to the
cos theta star used in Drell Yan AFB measurements. And then the the AFB the asymmetry is
calculated using this this variable
to extract the forward backward asymmetry. The measurement is done in the lepton plus jets
final state, with resolved and boosted topologies and
reconstructed through a kinematic fit
And here in fact
you can see cos theta star for different initial states q q bar, q g, and and
gg at the at the
simulation. And here you can see the reconstructed
template bins for cos theta star and TTbar and x f and then from the
fit we extract AFB to be zero point zero four eight. as you can see the measurement is dominated
by statistical uncertainties. And the result agrees well with Tevatron NNLO QCD and
CMS spin correlation measurements in the dilepton channel.
measurement is also used to, to,
to look at chromo moments of of of the top quark,
and place limits such that um
such limits.
And ATLAS obtained the first evidence of charge asymmetry in the lepton plus jets
channel again using the result on boosted topologies and using
run two data
and this time since this is
like forward central asymmetry, delta y variable is used and the result is zero point zero zero six
which differs four sigma from zero. And the NNLO prediction is zero point zero zero six four. The
measurement is also done in bins of MTT bar as you can see here compared to NNLO
QCD plus NLO electroweak predictions and POWHEG plus PYTHIA eight
predictions.
The agreement is very good both for POWHEG and NLO but it's it's it's slightly better for for
the NNLO plus electroweak NLO corrections.
The measurement is also
used to place limit on some coefficients of dimension six EFT operators
Um coming to spin correlations
um so, spin um
correlations
can be characterized by the spin density matrix which is parametrized by 15 coefficients,
which fully characterize the spin dependence of top quark pair production. And CMS
determined these coefficients by one D angular distributions at parton level and dilepton
channel. In addition to that, lab frame asymmetries are also measured, which are
independent to these coefficients. So, you can see
one of the comparisons of data NLO calculation NNLO calculation POWHEG and
MadGraph five with fxfx merging.
um all distributions presented in the paper and also the exacted parameters agree well
with the standard model. Also, um
limits on new physics is placed through anomalous couplings
and um spin correlations
are also measured by ATLAS
delta phi delta t and delta phi versus m TT bar in the dilepton channel again and the
fraction of standard model like spin correlations extracted in standard model
this is exactly one and for the measurement both um
templates are used for spin correlated hypothesis and uncorrelated hypothesis
and the measurement yielded one point two for nine um which which presents 2.2 sigma difference
between POWHEG and
PYTHIA prediction and data. you can also see this from the distribution here the
difference between the predictions and the data. So, this led to some alternative
predictions with NLO QCD plus weak couplings and also NLO QCD using an
expantial expansion of the differential distribution in powers of of the
couplings.
Here you can see these
predictions from NLO um expansions and NNLO expansions. And the extracted value of the
fraction using the NLO expanded template um comes out to be one point zero three which is perfectly
consistent with the standard model and POWHEG plus PYTHIA eight predictions and the NLO
predictions it is somewhat less consistent with
with the NLO prediction.
and the measurements are also used to place limits on top squarks in the hundred seventy two
hundred GeV range using delta phi in of delta eta.
Here I show the comparison of ATLAS and CMS measurements of the delta phi
at at the parton level also compared to
um main Monte Carlo
used in the two experiments. You can see there is a very good
agreement between ATLAS and CMS data points. And also very good agreement between
ATLAS and CMS main Monte Carlo predictions.
And we see there is a very good agreement with mg five mc at nlo with FX FX merging,
where we have two additional jets from the matric element.
And when you compare the measurements with the NNLO prediction,
there's some fair agreement. That's not not perfect. So these, these were the
first
ATLAS CMS comparisons for for run two and this
paves the way for the first thirteen TeV ATLAS plus CMS combination from TOP
LHC working group. TOP LHC group also made the first
full combination of the eight TeV data for W boson polarization from Atlas
CMS using both TT bar and single top combination using the blue method.
And you can see the results here W boson polarization fractions. And
they're compared to NNLO and the agreement is very well. Precision for f zero is two
percent and for f l it's two point five percent. And improvement in precision is twenty five percent for f zero
twenty nine percent for FL with respect to the most precise single um measurement. um the the combination
the combined limits for anomalous couplings, Wilson coefficients are also done. But
I'm not showing them here.
And
this brings me to my conclusions. So I presented new run two LHC top mass and
properties results with increased precision
new methods and new observables. um top quark mass combinations reach 500 MeV
uncertainty. And it's extracted from differential cross section measurements
including multi differential measurements differential measurements as well.
um it is extracted from boosted top jet jets and at an energy scale of four hundred eighty GeV, it's extracted from soft
muon tags and also
running off the top quark mass is tested up to one TeV. top quark width is measured using
full run two data, similar for Yukawa coupling. First TT bar forward backward
asymmetry measurement at LHC is presented and also first evidence of TT bar charge
asymmetry with full run two data and precise spin correlation measurements and comparison
between Atlas and CMS and ATLAS plus CMS W boson polarization
combination at 8 TeV are presented. and, in many of these measurements limits on new physics
are also placed.
So not all the results used run two data yet, so we'll have more precise and
varied measurements soon. And at run three, we expect two times more TT bar events and
at high luminosity LHC 20 times more um TT bar events. Therefore, we'll be able to make
more precise measurements and we'll have better understanding of the top
properties. And we'll have increased reach for new physics through direct searches
and effective field theory approaches. Thank you.
Thanks Efe for this nice overview over those results. So please raise your hands
to ask question, remind your name.
Yes, Francesco.
Go ahead. Thank you, Frederick. This is Francesco Spano from
ATLAS. Hi um Efe
Thanks a lot for summarizing
All this very rich harvest of impressive results. I was wondering about your slide
sixteen.
I mean, the forward backward asymmetry. So
my question is, how are the three templates defined? As you say they're
based on models of extensions of leading order three level cross sections? Is this
a leading order prediction? And so what is the impact of the modeling uncertainties
on these templates on the final measurement? And then I was wondering if
there's also any profiling on the uncertainties so it's three questions
sorry. Okay. So in fact it's a bit complicated if if you look at the paper later, so these
expansions so in the end, what is done here is to try to distinguish these
three initial states and the calculations are done so, the the main asymmetry
comes from qq bar and some from qg but not from gg and then these templates are
calculated using those calculations. So, this is I would say effective leading
order in the end so
but just to have some asymmetry it approaches next leading order
and um sorry what was the second question
if there is any impact what is the impact of the
theory uncertainties? Okay, I don't remember
the numbers but as you see now the systematic uncertainties are sub dominant here, but of
course we should have
we should really have large modeling uncertainty when we try to separate these
these initial states because it will depend on what simulation we do what cuts we
impose, etc. So that should be significant when we have enough statistics that that
I believe would be the main difficulty.
So you're not doing any profiling, right?
um, in the end I don't remember that, how exactly it is calculated.
But it's, you know, it's the template fit and
to um as you see in the plot, it's only shown qqbar and gg. And if you can separate these
we extract afb
any other questions or comments?
Maybe a I have very quick one. So in light of what Fabio showed
about the new latest developments on on the Coulomb resummation at the threshold in m
TT bar.
I guess this will have some influence on on your Yeah, your your coupling extraction
or your mass measurements that you presented, right? Yes, that we need to understand better.
But maybe at this level of precision it's not so important yet but probably
increased precision will have much bet we'll need a much better understanding.
Okay.
Yes.
I would um like to go ahead. Yeah. Hi, this is Nadjieh from um CMS DESY, just to just to
complement the answer by Efe. In the previous analysis, the asymmetry uncertainties are
introduced as nuisance parameters in the fit, in particular, the experimental
ones
Okay, thank you for the precision Nadjieh.