So
procreate is in adolescent.
Okay, so it started to show for making him have a full stop, but we'll start with
that first and then have CMS on the same topic then. So I'm going to talk about top
properties from from Atlas. So the top graph at the top here cross section at the
LSE is very large, it's 830 Vika barns at 13 gb. So in room two, we've produced over
100 million top 20 top pairs and the ATLAS experiment. This gives us a very large
data set to study for different particle properties of the top, and the production
mechanisms and the decay. So we study all the different parts of the top production,
and the top Quark itself and the top Quark decay, and all the properties of the decay
products as well. So firstly, we have properties related to production. So
obviously, there's a cross section itself and the kinematics of the top and the anti
top system. And for those, they're covered by the top by feature, and then there's
spin correlations, which are induced by the production mechanism. And there's the
charge asymmetry of those The top pair production, the top part polarization and
then flavor changing neutral currents and many more. We then have the fundamental
properties of the top part and which are the mass and the waves and which material
we'll talk about later in the session. And there's a charge and the spin chain
indirect measure. Then we have properties related to the decay of the top Quark, I
mean these are things like the W Felicity measurements, and charge electron flavor
violation and flavor changing neutral currents and various different decay
channels will be talked about by curl, and then jet shaping curl, color flow and
anomalous couplings and some more as well. And then finally, and because we produce w
bosons and top Quark this case, we can look at the properties of the W goes on
itself. And today, one of the analysis I'll talk about is the measurement of the
universality of lepton couplings to W bosons, and looking at the branching
ratios of W's and top events themselves. So there's far too many results to cover
and frontlets say today I focused on three different results. So there's the charge a
symmetry, and then the spin correlations between the top and the anti top. And
there's new CMS Atlas comparison plots for this. And then there's the measurement of
the inverse ality of electron couplings to the W boson. So firstly, the charging
symmetry. So at leading order and you expect the Tiki Bar production is charged
symmetric as a proton proton Collider. However, on higher orders, you get
interference effects in the Quark glue on the Quark counterpart channels, and also
electric contributions can lead to asymmetries. And so the main production
diagram is shown on the left here and for Q bar production where you get a deal and
on the S channel and then Tiki Bar and but there's also a box diagram and then when
these interfere, you get a charging symmetry, and also the SMT physics can
lead to large enhancements, and which makes this particularly interesting when
you do it as a function of kinematic variables such as the mass of the teacher.
Our system the glue and glue and process remains charged symmetric to all orders.
And this is the dominant production mechanism overall. So this dilutes the
asymmetry significantly. And the quantity we try to measure is called AC. And so
this is the number of the fraction of the time basically, where you have a top
that's more forward from the ante top minus the number of times you get the
answer top more forward from the top divided by that the total sets the
essentially the fraction of times you get top more forward. And and positive values
indicate that the top is more forwards on the top which is what we expect. So not to
scale this is what we kind of expect you expect to see a slightly more and narrow
empty top into distribution the top and therefore you get a slightly positive
value of AC. The analysis as I mentioned, is done in different kinematic regions as
well as inclusively. And so first There's a result analysis where boosted events are
removed. And a BDT is used to assign the different checks to the two top systems,
including Cale Fisher as a massive fan tronic top and W in various Angular
variables to assign different jets to different top to the top and the anti top
such that both the top and the anti top can be reconstructed and then they're
calculated. The best combination is used and only events of good reconstruction
according to the BDT which are attained.
Secondly, there's this boosted channel which gives access to the highest kinetic
regions particularly an empty bar and a high PT and the hydronic top so we're
looking in some electronic events one electronic components are drawn. The
hydronic top can be reconstructed with a single large radius jet and we require the
PTS to be greater than 350 gV. We then use two variables the mass of the jet to
distinguish it from HD and also this variable called tau three, two and a nice
to flop show. Okay, three, two in a QC DJ selection on the right hand side And you
can see that it peaked at high values. And then enter Tiki Bar and booster jet
selection on the left hand side where you can see the white which is the Tiki Bar
component has a large tail to low values of totally unusual events that you'd
select using this tagging of hardrock tops for the electronic side and you can use
the ETS and the leptons and an R equals naught point fortune to reconstruct the
top under the assumption that the W is on show. So, results are presented for an
inclusive volume AC and we find not not not sex with an error of not point naught
naught one five and this is for sigma from zero. So this is first evidence of non
zero charge asymmetry in Tiki Bar. A PP collider is in good agreement with an nll
calculation. And additionally, we unfold into bins in in the mass of the TT bar
system and also in the longitudinal boost of the TT bar system. So these two blocks
here, the left hand block Gerry's AC on the y axis as a function of five different
variants of the mass of the Tiki Bar system. And you can see the asymmetry grow
slightly as you move to higher tiki bar and the green is the next next leading
order prediction plus another one electroweak and the data agrees Well, the
right hand block says the same thing, but because along the tutorial groups and
again for the Korean to see. So, having seen good agreement with the standard
model, we go to set limits in an effective field theory and based on both the
inclusive and the left hand side plot here and so, now you should see the variable C
and which is one of the linear combination of the Wilson coefficients and which
affect the charge a symmetry under a flavor symmetric couplings scenario and
you can see near the just you can see at the bottom to previous results and then
the inclusive results and then the different MTT bargains included Results
provide very strong limits as to the 1000 to 1500 gd, then and higher volumes of
mats we start to run up statistics and lower volumes or lessons. Moving on to
spin correlations. The standard model predicts the top Quark pair should be
produced without polarization, but with some correlation between their spin
states. As the top part lifetime is much shorter than the spin D correlation time
the spin information is directly transferred to the decay products. And the
analysis done with a simple electronic Tiki Bar selection requiring one electron
one neuron and greater than one greater than or equal to one reject. And we then
look at the angle between the leptons in both eater and phi, but delta phi is the
most sensitive. And this is sensitive to the spin correlations and this is seen in
this plot. And so if we just look at the two lines, the blue and the red line, so
the red line shows the delta phi distribution that you'd expect if you had
noticed correlations between the top and the anti top. And the blue line shows if
you had the standard model and correlation between the two. And so, you can see that
this variable is highly sensitive to the spin correlations. So results are unfolded
to both parts on level and also particle level distributions are really leading
uncertainties on the inclusive measurements come from generator modeling,
mainly radiation and scale. The data didn't show slightly higher spin
correlations on the predictions, and this is quantified by fitting templates of the
fraction of the Standard Model spin correlation, and one minus by a fraction
of the Standard Model correlation and no correlation and using the perfect next
leading order prediction, and we get about 25% more correlation than we'd expect in
the standard model using this thing. So this is the distribution of the delta phi
that's been unfolded normalized cross section on the left hand side You can see
that the data is consistently high at low values of delta phi and consistently low
at high values of delta phi showing a slightly stronger correlation in the
spins. And then the predicted by the next leading order Monte Carlo shown in this
plot
the right hand plot and shows the same thing. So it's the ratio to power a
Bezier. And on the y axis, and the data is the same as the left hand plot. But this
time, we've added in a next to next leading order prediction. And you can see
that some of the, the discrepancy is reduced, but it's not entirely solved by
this and there's work on going on more accurate calculations and comparisons and
to the theory in this area. So as a discrepancy was seen, and this is not
completely understood. And it's interesting to compare to see if CMS see
the same thing. So CMS has also produced measurements of the delta phi distribution
from 2015 and 2016. And you can see on these blocks and red, there's the CMS
data. And in blue, there's the Atlas data. And you can see that the CMS and the Atlas
data agree very well. And we also check that the two simulations that we use agree
very well, and these two as well. And so we've produced, these are not
combinations, but these are more comparisons, showing that the two, the two
collaborations are producing very similar results in these distributions. Moving on
to the third analysis, and this is the electron universality in w two leptons in
TT parlance. So the universality of the coupling of the different generations of
leptons to the gauge bosons is the fundamental axiom of a standard model. The
large number of Tiki Bar events produced at the LSE give us an excellent sample of
W bosons to test this. So this analysis looks to measure the ratio of the
branching ratio of W's to toes divided by the branching ratio of W's to means And
the motivation for this is that we want to test this fundamental axiom, but also that
in previous measurements and discrepancy has been observed. So, the left and four
experiments did a combination of their different results and their combined value
is 2.7 sigma Hi, in this in this in this body. So this plot here shows a comparison
of different previous experiments measurements. So, the bottom panel plot
shows who retires divided by the least means, the middle panel who retires
divided by w two electrons, and the left points in red show high for both of these.
And the top panel shows and whether a much more accurate measurements that ratio of
the two light laptop generations and there's now Atlas and ALEKS TV and lab
results and ch CDF or have a very high precision here. So, this is generally
Well,
Mark better understood
So, events are selected and with the Thai jets and electrons, and this is triggered
by an electron or Mian. And with a second leptons, which is always a meal, the
branching ratio of times to neurons is very well known so that we can easily
extrapolate from the number of events where we see a W going to a time going to
a Mian and divided by the dope branching ratio of W straight to me ons to the
branching rate to the quantity we're interested in, we're w k times divided by
w, because the the second part of this sophistication is very well known. So
events with new ones from time to case are distinguished but those were the mediums
are produced directly from the W by their softer PT spectrum and the displacement of
the decay. And the displacement is characterized through the transverse
distance of closest approach to the track and which is d zero. So this plot here
shows the zero and millimeters on the x axis and the events and you can see in
light green In the case where they have a prompt neon, Adobe, neon coming directly
from Adobe, and then dark green we have where the tires that came to me obviously
we have a W two. You can see there's a clear distinction between the two the two
cases. to model this distribution well the D zero distribution for the prompt me on
just taken from templates created from said to die new events and so you have
prompt new ones that decays and therefore you can take the distributions from data.
And the distribution for nonprofit beyond service immune from tires and wheels from
heavy hug on the case is corrected for using the measure of resolution of t zero
in the same selection.
You have two minutes.
Yep. So the main backgrounds to the analysis are said to dine yawns plus
Jetsam the diamond on channel and we will indicate a nuance from hadron to case. And
so for the diamond background effect of the diamond and the mass spectrum is used
to normalize this background with the same check requirements and for the new ones
from hadron the case. Same sign and chart selection is used to normalize the
background of neurons from hadron the case. And and then a simulation is used to
extrapolate from the same sign to the different sign and selections. And the
right hand block shown here shows the same sign selection of this D zero variable
showing that as well model in the same time region. effect is then performed in
three bins and PT and multiplied by eight bins and D zero and the two channels so
it's a tag electron or a type neuron and an appropriate arms in both cases. Good
agreement is seen in the fitted distributions and you can see four of the
PT bands here. And whereas is that to to lower PT ones on the top panel and then to
higher PT ones on the bottom panel and a new channels and new channels. The fitted
value of r is found to be naught point nine nine to plus or minus 1.3%. And so
this is in good agreement with one is the most precise measurement to date by a
factor of two. And it's after the error of the of the lead measurement and the
Standard Model seems to prevail. So now we can look at look at our universality plot
again. And we can see in the bottom panel, we now have our new Atlas results, sitting
sitting nicely on one, and showing that the Standard Model postulation of equal
couplings seems to work well. And then
the old results as well, so shown from this book.
So in conclusion, Atlas has measured many different properties of top quarks, and
now w Verizon's and Tiki Bar lamps. We've heard many different kinematic and
fundamental properties in the sector. And so far that standard model has described
the data extremely well. More results with the wrong two data sets are in the
pipeline, and wrong three and beyond promise even larger data sets. And so
there's many more exciting top physics results still to come. And then As with
the previous Speaker I've set up a private Zoom Room in case there are more detailed
questions at the end of the session.
A lot, Chris, any questions?
Ask one quick curiosity question.
If you go to slide 15, you didn't mentioned you estimate volumes that come
from attorney case. But I was wondering whether how much of your sensitivity Yeah,
if you go to previous slide still 15 Yeah. How much of this STP comes from the last
thing because you seem to either run out of statistics predict your background in
the last thing for me. And I would increase to expect that it's not So
quickly diminishing because, you know, these are heavy flavored decays, and they
would have large impact.
In the next slide, a data driven
Yes, so this plot here is the high PT Ben. So maybe if I go to slide 17, then we see
the middle and high PT ranges. And so the top plots here show 10 to 20, gv, and then
the bottom flops are higher than 20 gV. So the hadron decay background is mostly
important at low PT and it becomes increasingly less significant as you move
to high PT and then you end up simply running out of statistics and the towers
and that becomes the the uncertainty. And so the hadron decay background is very
important and it's particularly important in the five to 10 gV benefit chain, which
I don't show here. And in those cases, we do have statistics open to the Heidi zero
tell and we can that both the simulation and the simulation is modeling the shape
of this right and we can normalize the distribution in our control regions in
this case.
Okay, thank you.
Any other agent question?
If not, let's thank Chris again.