Okay, so good morning everyone. I will talk about CP violation in B decays.
Okay. So first a brief introduction. We know CP violating observed in k, B and D
meson decays, and they are well consistent with CP standard model prediction,
but they are still too small to explain the absence of anti-matter in the in the
universe. So more searches are needed. This slide will will show the
two analysis one is about Lambda b to p 3 pion , the other is B to three pion decays.
For the Unitary triangles measurements, please see the talk from Mark
tomorrow. About Lambda b to p three pion decays. The previous measurements
shows a 3.3 sigma for CPV using the triple product asymmetries. This
measurement performed in the regions of phase space. So we will update it with more
data set to see if this is true or due to statistical fluctuation. For the new
analysis of this decay is updated using 6.6 inverse feta, inverse feta bar data. and
about 27 thousand yields observed which is about four times than the
previous and two approaches are exploited. One is triple product asymmetry use with improved
binning schemes. The other is unbinned energy test method. You can see the
clear signal on the right plot. The trip products are constructed in the
mother particle rest frame and using momenta of final three particles in the lambda b rest frame,
or the lambda b bar rest frame using the corresponding anti
particles. And then we can construct the p-odd asymmetries by comparing the
different sign of the CT for the lambda b decay, and correspondingly compare
comparing the the the signals with different sign of the CT bar for the
lambda b bar decays. After that we can construct the CP violating or the P
violating observable observables as the difference or the sum of the AT and AT
bar. That's shown on the red or the blue boxes, so, how to to get the improved
binning schemes. First we developed an amplitude modes based on these two theoretical
papers and, and then we can introduce. So, first we have model which which is
can reproduce a similar phase space distributions as data observed from the
previous measurements, then we'll introduce the p-odd CP violation, that might
from could from the S and P wave interference as shown in the following
decay chains. The lambda b to N star plus one half and N star plus three half
the phase space region of this decay allows for many N star plus and Delta plus. So, this this
model actually is an approximation of the nature. So, we can do sensitivity studies
based on using this model. With this model, we have a new improved the scheme A
which which is for the phase space division in the polar and the azimuthal angles of the
proton in the Delta plus plus rest frame, or the Delta plus plus in the N star plus
rest frame. We also have a scheme B which is which is based on the absolute
value of the Phi angle defined by the two decay plans. We keep it we use it
because this is a this is this is the same as the previous measurements we want to
check if the symmetries are still there. So,
for the phase space integrated measurements, the acp is consistent with CP symmetry you
can see from the top, then the the ap variables, there is about 5.5 sigma deviation
from the p symmetry. There's Parity violation here. For the measurements in
the different regions of phase space, the sample first split into two samples.
Sample A is for the a1 resonance dominated events, sample two is for the
multiple N star dominated events. As you can see from plots, the first two plots
are for the a1 top two plots, then the bottom two plots are for the N star plots, dominated
events. The red point is for the acp oberservations and the blue points for the
ap measurements. There's no evidence for the CP validation, the highest
significance is about 2.9 sigma, as you can see in the scheme B on the right,
bottom right plot. So for the energy test, energy test is a model-independent
unbinned test, which is sensitive to the local difference between two samples,
which might which might from the CP violation. The statistical test is about
three terms the first two terms are calculation in two samples separately
and the third is for calculation between two samples. The weighted function has two
parameters. The d parameter is the distance between two candidates in
the samples, which is determined by in the space determined by the decay topology
and delta is distance scale can be optimized from the Monte Carlo. The total
sample are divided into four sub sub samples according to the transformation
under the charge and parity transformation. So, we can do the P-odd CP
test by comparing sample I IV versus sample II III. And also P-even CP
test by comparing sample I II versus sample III IV. And also we can do
parity test. By comparing sample I III and the sample II IV
So from the Monte Carlo we have.
We can have three kinds of delta values, then do the test shown in the first in the
previous slide. For the P-even CP conservation test as shown in the blue box.
The highest significance is about 3.0 sigma corresponding to a
delta value equal to 2.7. After combining these three measurements,
the significance is less than 3 sigma. So unfortunately, here there is no evidence
confirmed. For the P Conservation conservation test. The first two test has more
than five sigma. And when combine all three measurements and the parity test
is about 3. 5.3 deviation from the parity conservation. So, here's
the parity violation here. About B to 3 pi decays, the previous analysis
show, shows the raw symmetry localized in regions of Dalitz Plots as you
can see from plot, the colors for different values of the asymmetry.
which may come from the low mass S-wave contribution and rho interference, or
the rho omega mixing, all pipi-kk rescattering. So, an amplitude analysis is
needed to find the correct source of the CPV. For the amplitude analysis, the
models models are built separately for B plus and B minus. And they are two kinds
of parameters the C is complex coefficients for the CP violating and an F is strong
dynamics part, contains the lineshape and the angular distributions
and is CP conserving part. There are three different methods
to describe the S wave contributions, the isobar model, K-matrix and the quasi model
independent approach. And then we construct two observables, the ACP for the
CP violating measurements by comparing the squared
the coefficients And the fit fraction as the integral of each contributions,
so about 20
thousands signals constructed using three inverse feta bar data. And you can see
that there's different structures in the Dalitz Plot. Obviuously the red box
corresponding to to the low resonance, or might rho omega mixing here. And also there's
f2 probably in the plots and also might pipi-KK rescattering. So, from the
numerical results, we can see that the dominant contributions are from the rho
770, which is about to a 55%. And s-wave about 25%. There are larger
CP violation from f2(1270), about 45% and from the s-wave about 14%. But
there's no asymmetry from rho(770) which's large contribution in the
decays, both three methods give the consistent results.
For the rho(770), if you look at the symmetries projections in the cosine theta,
helicity dangles and also the mass. There are small very small asymmetries
almost consistent with zero. But if we look at the asymmetry projections, below, and
above the rho mass, you can see the clear asymmetries and asymmetry change the
signs crossing mass, cross rho mass. If you put them together the
asymmetries cancer perfectly. this characteristic pattern is due to the SP
wave interference, which proportional to the cosine the helicity. So when
integral over this angle, asymmetry vanishes. That's why we cannot see the
asymmetries for the integrated measurements. And also we'll find
first observation for a CPV in the process involving intense f2(1270) you
can see the larger asymmetries from the from the plot. A large plot CP
asymmetry can go to 40% and there's a small discrepancy between
the mode and the data in the mass of the f2. afters some systematic studies the
this CP violation here is robust.
For the s-wave results,
these three approaches are well in good agreement. And if you look at the left
top left plots for the squared amplitude and
if you look at the
top right plot, this is the phase of amplitude model.
The phase is hard to describe because due to different assumptions here and also
here is clear that you can see there's no f0(1500) are in the isobar model. And
also this comparison can be made by by split B plus and B minus. So as
shown in the bottom three plots, is clear that there are similar CPV
pattern for these three approaches. Like, for example, the, the there's larger
asymmetries in the low mass region. And the asymmetries change sign when the pipi
mass goes to one GeV which is corresponding to f0(980) and also the and started to
change a sign from if mass larger than one GeV. So, so there is last page, the summary.
So, these multiple decays are an interesting place to search for CP
violation, because the rich phase space structures allow, allow to, to to improve
the sensitivity for CPV and parity violation observed in Lambda b to p 3 pion
decays, but we didn't confirm the evidence of CP violation. So the more data are needed
to do further studies and we found the several sources of CPV in B to 3 pion decays.
The new CPV the pattern of the rho(770) and the CPV found in process was
a tensor tensor f2(1270) and CPV in ths s-wave contributions in the low
mass regions. That's all. Thank you.
Thank you very much Jinlin, was very clear.
For questions, so please ask people to use the hand raising feature from
raise your hand on the application, if possible, if you can't put a comment in
the chat. And we'll try to get you to speak at the right moment. So is there any
question for the speaker at this time?
Maybe to start
since I don't see any hand. I have a comment on the first analysis on Lambda b. Sorry, in your first paper
using the same channel you publishes in nature, yes, you publish the
evidence for CP violation and know nothing, let's say for P violation. Now
you use a same qualities partially correlated with the first one, and you
have a bit less than three sigma for CP violation, I don't think is the issue
since you moved from three point what was 3.3 to something, let's face it, it can be
of course, due to the statistics, but you have now five on five sigma for the
P violation. So I have a couple of questions. So did you check the
compatibility for these two analyses that that that use the same final state? For
example, you may be you did? Okay, you could try to perform the old analysis
on the new data set the total sample that you use now or vice versa in order to in
order to see if you have agreement or not since moving from no evidence to 5.5 sigma
for violation, I think that is a bit strange.
Actually, we did some comparisons separately for for the first example, and
the second samples also applied the same same selections. Found actually there's
there's about 2.6 sigma consistent between two to two samples. So we think that this
is due to the sense of statistical fluctuation for the CP violation, but
for the parity violation, and we think that this is Due to the we have the
larger statistics, so we can find that it's is about 5.5 sigma
deviation.
Okay, thank you.
I would have a question if I can.
Yes Luccia go ahead. So this is more referred to the second measurement, you show
B to the 3 pions . So it's great to observe new sources of CP violation.
My question about these is, can you get any CKM information from this decays?
I don't think so. Because here is the phase that actually is associated with the
resonance or rescattering? So, in this kind of level, I don't think it's direct to the
CKM angles.
Because when when you construct the amplitudes
when construct the amplitudes actually this is on the hadron level. So, the phase
is not direct to the CKM angle.
Okay, thanks.
Okay. There are no other
burning questions so we'll move to the next talk. So we're still on time.
All right, thanks.