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Yes. Okay, good. Can you see my shirt
next? Okay. Very good. So let me can you

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can put the screen. Yeah. Is there okay?
So thank you very much it's honor for me

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being here talking about soft probes at
the LFC. I have basically two objectives

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on this talk. The first one is to
demonstrate that the study of soft probes

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in heavy ion collisions allowed to make
precision measurements on the hot and

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dense medium. That we produce in heavier
in collisions, which is called GGP. These

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because having higher energy densities we
can study efficiently collective phenomena

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like radio dynamics, a traffic flow, given
the fact that we have large multiplicities

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we can start with Statistically neutral
particle productions with with a

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statistical approach which is in its grand
canonical formulation, and then we have

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large or large systems. So, we can
disentangle hydronic phase effects which

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can which can be also dialogue through
centrality, for example, studying nuclei

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formation or kinetic result in case of
coalescence or the disappearance of short

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living resonances theory scattering. Now,
the second objective of this talk is to

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show how exploiting exploiting small
colliding systems we can have a better

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understanding of what happens in heavy
iron conditions because recently we

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realize that simple hydronic interactions
as proton proton are far from being

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Elementary, you need multi party
interactions to explain multiplicity you

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need to make crosstalk between multiple
interactions in order to explain the

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hardening of the spectra like for example,
color recognition mechanisms and you need

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the pattern density fluctuations in the
initial state in order to explain final

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state phenomenon. Now for many of these
details, they lead to the talk held

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yesterday by Valentina. But this clearly
raises two questions. The first one is, if

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we can use more systems to better
interpret large systems observations, and

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I will talk a little bit about this. And
if this implies cued up formation is more

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systems, I will not address this a Li.
Tomorrow in a perilous session. Now let's

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start from Hunter abundances. As we
probably all know, the production of light

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flavor hadrons can be described Yes, it
can be described by the statistical

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modernization model in central javion
collisions in its grand canonical ensemble

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formulation

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squadrons, basically

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can be seen as coming from a hot hardware
restaurants gas in thermal equilibrium.

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And you have here this famous flood plot
from the Alice collaboration, which shows

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over nine orders of magnitude to
production of particles from fires to anti

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Union for that actually the the
statistical models can reasonably well

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describe these yields and the parameters
which come from these feet are the

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biochemical potential which has a DHCS
zero and a chemical result temperature

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which is around 153, which is by the way
compatible with the Kira crossover

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transition temperature from like Sq CD.
Now, there are details in this description

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for example, the fact that short living
resonances cannot be described, and so

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they are not included in in the thermal
fit because of the influence of a drink on

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Ronnie Chris gatoring. For restaurant for
short living residences, Denver is of

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friction with protons like you can
visualize here which is being addressed

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through the s matrix approach in order to
take into account piezocone interact

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interactions and other approaches actually
try to solve the proton at the same time

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the Xi issue with the flavor dependent
chemical freeze out temperatures. Now,

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another notable point is the fact that
loosely bound nuclei and anti nuclei are

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actually very produced by the statistical
model which means that they are they're

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compatible with thermal production and and
these leads to the question why so,

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loosely bound states can survive the
chronic phase and they can come also from

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coalescence model so, that we will discuss
later. Now, how do these yields compared

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to what we measure in small systems were
here we come to the famous blog which was

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also showed nicely by Wilk in the first
talk, which is the high turnover pion

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ratio as a functional multiplicity for
different particles for different hadrons

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from broken proton at very low
multiplicity to heavy ions of high

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multiplicity. And what one can observe is
that the hovering over biracial smoothly

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evolves across multiplicity reaching the
terminal values in that lead. Now, these

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behavior is not square root of as the
pendant down actually to topic energies.

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And this is also shown by this new
measurement for this conference from the

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Atlas collaboration which shows the study
of size as a function of multiplicity in

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proton proton collisions at five TV as
compared to the seven and 13 TV show we

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know the final square root of s and it
depends on the hadron that we are

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considering. So, the stranger the
headroom, the steeper the increase and it

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is the perfect yarmulke here. Now, there
is a caveat here that the fact that also

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nuclei in house with multiplicity, but we
will discuss this later. So, but this is

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why we normally talk about these as
strangeness enhancement in small collision

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systems. Now, what is also important to
show is that for high multiplicity broken

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protocol collisions, the Hydra chemistry
that we measure is actually roughly the

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same as the one that we have in a fully
thermalized system. Now, how can we

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interpret this trend? Well, we can try to
use models which are normally used in

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large systems and extend them to lower to
smaller systems. Or we can do the other

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way around. So use, let's say in backhoe
modernization models like PTR DC and

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expand them to large systems, or to use
the two component models. So, let's try to

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go through these possible explanations.
So, first of all, is first of all thermal

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models statistical idealization models in
order to try to describe The multiplicity

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of dependence of hydrogen production, what
can be done is to consider canonical

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suppression which means that the quantum
numbers of the system which are charged by

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reason and strange numbers are forced to
be conserved in smaller and smaller

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volumes as the multiplicity decreases. And
as you can see here, you can have a

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qualitative, let's say, reproduce fraction
of what is seen for cyber by an omega or

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pi, but there are clear problems for
protons counts and especially for files

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which do not which are not affected by
canonical suppression, but buyers are for

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the charge

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for charging quantum number, so, this is
why this is increasing this way a low

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multiplicity. Now another possible way of
using the statistical learning is a model

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for small systems is to introduce an under
saturation parameter gamma is which is can

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take into account an incomplete
equilibration of the strange quarter. Now,

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in this way one fits each data point for
each system fits gamma is the the chemical

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freezer temperature and the volume and
this ends up to be better in agreement

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with with cascades for example, but still
with the large frictions for protons.

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Now, the other way around as I said is to
try to use more collision systems as sorry

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smaller system MonteCarlo models to
describe the evolution with multiplicity

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and this is what was tested for PGI, eight
and Dipsy and the general. The general

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outcome here is that the fact that these
models can qualitatively reproduce barrier

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enhancement with multiplicity, introducing
color ropes, which means that if you have

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densely packed strings, these leads to
higher strength, tension and solve the

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more probable to produce variants with
respect to to the masses. Now, this is a

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possibility of course, but in this new
measurement from the experiment of phi to

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new new word for word rapidity as a
functional multiplicity and for lo PT

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reported here, one sees that actually
ropes seem not to be the dominant

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contribution at low PT for the yields of
five for example, the other way to

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describe the Hannover pion ratio is a
function of multiplicity is to use two

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component models like CT Corona and in
these models, you have actually two

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regimes a double regime each coalition
which is one party can be called core,

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which is identified by high density the
key GP formation also in small systems,

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possibly also small systems and
thermalized organization which is dealt

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with in the grand canonical limits. And
then you can have a Corona which

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corresponds to the lower density in the
initial state, which hydrolyzes through

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jets in a vacuum, and this is dealt with
with string fragmentation. Now here I

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report two results from models from the
equals model on the left and the CCI model

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on the right, which shows actually that in
these models, the handler firing ratio is

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actually flat as a function of
multiplicity, but it has two different

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values, one for the core and the other one
for the corona. And the increase for

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example of the omega over pi ratio is a
functional multiplicity comes from the

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change in the core to Corona ratio as the
multiplicity increases. So for high

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multiplicity, the core contributes more to
the final multiplicity, while for low

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multiplicity, the corona contributes more
and you can see that these two components

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model do a good job in reproducing this,
this trends. Now, in order to test these

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two component models, what one can do is
to try to classify topologically proton

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proton events and this is what was tested
by Dallas collaboration. You can divide

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each event in a two word region and away
region and a transverse region towards

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means basically the direction of the Jets
which is proxied by the ISP t hadron in

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the event which we call PT leading. And
this has to be larger than five gv because

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of the jack pedestal effect which was
reported, for example by Alice and Alice

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but also from CMS at the LSE, actually,
which means basically that when we fix the

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BP leading being higher than five gv, then
the underlying the event multiplicity is

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not any more dependent on this heart scale
fixing Okay, so this is why we asked for

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bt leading or being larger than five gv
and then dividing the event in the toward

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region which is the direction of the
object in the away region, which is the

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direction of the recording jet if you want
and then a transverse region which is

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mostly dominated by the underlying event,
one can start particle production as a

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function of multiplicity of the underlying
event and the multiplicity Underland

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underlying event, we call it R T. And it's
the ratio of the charged particle in the

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transverse region with respect to its
average. So tuning our T means really

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going from E like event, having got t
equals zero going to lead lead like event

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going to RT equals to infinity. And the
result here that I selected is the Xi over

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pi ratio here is a function of PT, but
it's actually valid for across all PT. So

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it's also translatable in yours for Xi
over by ratio in the transverse in the

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right and in the toward regions in the
left. So let's first concentrate on the

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transverse region, which is dominated by
the underlying event. And what you can see

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here is that if we go from low
multiplicity in red to the high

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multiplicity of the underlying event in
blue, we see no strangers and how In the

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transverse region, so, where the
underlying event is selected, we observe

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no strangers announcement as a functional
multiplicity, while if we go in the region

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of the underlying event plus jet saw the
toward region here we can see an evolution

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and actually this evolution at high
multiplicity saturates at the level that

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we measure in the transport region.

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00:13:22,260 --> 00:13:27,690
So, in two components model this could be
explained as two different cyber biracial

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one in the in the in the jet and one in
the underlying event and the evolution

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that we observe in the reward region comes
exactly from the different importance in

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the final multiplicity between core and
Corona as a functional multiplicity, of

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course, for this we need more measurements
to draw a final conclusion. Now, as I said

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also, nuclei enhances the functional
multiplicity and is shown for the U turn

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on left and the new three and then Triton
on the right with new original From the

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00:14:00,810 --> 00:14:06,360
Lab at a TV from Dallas experiment, and in
this case you have strangers equals zero.

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00:14:06,360 --> 00:14:10,530
So, what causes this enhancement? Well, it
could be a lifting of canonical

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00:14:10,530 --> 00:14:14,940
suppression as we discussed before or it
could be called lessons probability that

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00:14:14,940 --> 00:14:20,250
kinetic result and this here you have the
comparison with models and you can see

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00:14:20,250 --> 00:14:24,270
that actually there is a qualitative
agreement in the sense that molders can

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00:14:25,230 --> 00:14:30,120
envisage enhancement as a function
multiplicity, but the quantitative

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00:14:30,120 --> 00:14:36,570
agreement especially for helium three, is
really lacking some precision. Now, going

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00:14:36,570 --> 00:14:41,490
to collective motional particles, well, in
a nutshell, it was already explained. So

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00:14:41,490 --> 00:14:46,620
let me be quick on this. If you have in
the Hydra picture, if you have ugp

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00:14:46,620 --> 00:14:51,090
formation, you expect to have radial flow,
which is a common expression velocity of

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00:14:51,090 --> 00:14:55,590
Barton's and it translates into pity
spectrum modification. And then you can

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00:14:55,620 --> 00:14:59,670
have Anisa tropic flow which means
basically translating the initial partial

167
00:14:59,760 --> 00:15:04,470
result trapeze into final momentum on his
Trapeze and the characteristics of the

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00:15:04,470 --> 00:15:09,180
medium the properties of the medium affect
how efficiently this translation is done.

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00:15:09,330 --> 00:15:15,000
So, low balk and sheer viscosities can
translate into larger rajal and unlimited

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00:15:15,030 --> 00:15:19,110
tropic flows. And then so, tropic flow is
measured through Fourier expansion

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00:15:19,110 --> 00:15:25,710
coefficients of the t distribution with
this values that we call v n. So, v two v

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00:15:25,710 --> 00:15:30,600
three before and so on. So, one thing
which is important to note is that initial

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00:15:30,600 --> 00:15:34,980
anisotropy can come from geometry. So, for
example, so, the centrality of the

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00:15:34,980 --> 00:15:39,960
collision in a V is but also from parts of
massive fluctuations in the initial state.

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00:15:40,710 --> 00:15:45,780
So, let's start from radial flow we know
from the IHC and also from break actually

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00:15:45,780 --> 00:15:52,020
that when when we go to more central
collisions, the spectral identify particle

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00:15:52,020 --> 00:15:56,730
and identify particle in this case of
problems for example, for lead collision

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00:15:56,730 --> 00:16:02,160
or fight TV get harder, okay. So, the
average As a functional multiplicity in

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00:16:02,160 --> 00:16:06,840
this case for the different species
increases, and this can actually be

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00:16:06,870 --> 00:16:12,720
described by hydro calculations and
another observable in this case here on

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00:16:12,720 --> 00:16:19,350
the right is the vanover Mason ratio is a
function, which is actually more like a

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00:16:19,350 --> 00:16:26,430
higher to lower mass ratio as a function
of PT, which shows this bound by the

183
00:16:26,430 --> 00:16:32,340
intermediate PT, whose increase is
actually fairly well described by hydro

184
00:16:32,340 --> 00:16:37,920
calculations. So, we have this hundred
over with this burden over measuring ratio

185
00:16:37,920 --> 00:16:42,900
which is described by hydrotherapy in
large systems. Now, we can go to small

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00:16:42,900 --> 00:16:48,930
systems and this is the new result from
the collaboration in a BP five TV versus

187
00:16:48,930 --> 00:16:52,950
multiplicity for size and omegas. And you
can see that actually you observe on

188
00:16:52,950 --> 00:16:59,040
hardening of the spectra also is more
systems. This is also verified across

189
00:16:59,070 --> 00:17:07,410
energies. And also in pilot. So, one can
also plot the lumber case you're short as

190
00:17:07,410 --> 00:17:12,870
a function of BDS it was done before, but
now for VP on left p lead on middle plot

191
00:17:12,900 --> 00:17:17,400
and lead lead on the right. And you can
see that qualitatively you have the same

192
00:17:17,400 --> 00:17:21,930
behavior, but with different magnitudes,
but then if you select specific key

193
00:17:21,930 --> 00:17:26,490
regions, so, in blue, the low PT in red,
the intermediate PT and in green the high

194
00:17:26,490 --> 00:17:30,660
PT and the evolution of this lambda work
is your short ratio as a functional

195
00:17:30,660 --> 00:17:33,660
multiplicities moves which makes the call

196
00:17:33,899 --> 00:17:38,759
is there radial flow is more collision
systems. Now, the application of hydro far

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00:17:38,759 --> 00:17:42,719
from equilibrium is under study Actually,
there was this nice presentation from work

198
00:17:42,719 --> 00:17:49,349
at the beginning. But considered it also
PCI with color connection can describe the

199
00:17:49,349 --> 00:17:54,929
low PT trend observed MPP. Now, an
important thing is that actually this

200
00:17:55,139 --> 00:18:01,349
lambda work is zero short ratio has this
evolution only In the underlying event is

201
00:18:01,349 --> 00:18:06,329
more system. So, you can see this in blue,
when measured in the underlying event this

202
00:18:06,329 --> 00:18:11,789
super imposes very well to the inclusive
measurement while the inject lambda

203
00:18:11,789 --> 00:18:16,589
lowercase your short has a much milder
evolution to more evolution also in led

204
00:18:16,589 --> 00:18:20,759
led collisions that you can as you can see
here, so this is actually characteristic

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of the underlying event is more system and
call it that the bulk of the event also in

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large systems. Now another important point
which was underlined yesterday by was

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discussing for the chance sector by john
McCallum before me is the fact that there

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are striking similarities between light
and heavy flavors for the London London

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work is your short compared to the lambda
see over the zero. Now, this is an

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intriguing observation because this could
point for example, to a perfect

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hybridization, let's say I hide
unification say of charm, but it is

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actually hard to believe small systems and
it's probably not even support By what we

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observe in large systems, where we see
here see at low p d for the v2. So, we

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have the v2 of her charges hadrons which
is larger than the V q of dimensions and

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larger than the v2 of of jPi for example,
and also the lambda work is your short

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ratio is larger than the lumberyard is
zero in javion, which points in heavy ions

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to our non perfect equilibration of charge
in the system. So does so why is most

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systems this could lead to this very same
bar in our Mason ratio. Now this probably

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challenge and also the hypothesis for
light flavors MPP for this for this

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specific measurement, is it called SSL
intermediate equally be explained by

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choleric connection. Now this this is of
course, on the development and also on the

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server this zero results with smaller
security would actually

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be very profitable.

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Now coming to an Enzo tropic flow on The
left you have a figure which is quite an

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old one, but it's a nice combination of
first results from LSE. Together with Rick

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results which shows v n v two v two v
three and V for now we are up to eight

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more, which is different from zero and
it's specifically in cemetery for

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collisions as in the Hydra picture. And
actually this can be reproduced by hydro

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calculations for the different centrality
This is for from the Atlas data points for

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the v2 v3, v4 and B five and this can be
reproduced by hydrocarbon nation with an

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almost perfectly we don't eat over so 0.2
now, we can also measure the v2 for

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different particle species. And what we
observe is that at low PT we have mass

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ordering. So the higher the mass the lower
the v2, and this is known as an interplay

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between rather than electric flow and if
you go to intermediate, PT or large Pity

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if you want you have an approximate
article by grouping which means that if

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you have higher number of Quark content,
then you have higher v2. And this is a

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compliant with a core coalescence as
dominant particle production mechanism in

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this video reach. Now, the fine mesons
peeve also here because it follows the

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mass ordering at low PP bunching with
protons with very similar mass and mass

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which is lying to mass on so for higher
VP. Now the mass ordering is also verified

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at the LSE up to the neutron and even
three as reported in this plot here from

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the eyes collaboration. Now, in small
steel, you got four minutes left, thank

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you very much. So in small condition
systems, the v2 was measured quite some

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time ago by the CMS collaboration and the
Atlas collaboration as well here is a

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combination of PPP LED and lead lead
results for the sole for the v2

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measurement. Also very recently, a very
interesting publication came out from

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Dallas collaboration reporting, v2, v3 and
v4 as a function of the multiplicity for

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led lab seen on Xenon v LED and BP
Coalition's and what is shown is that

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actually there is the here RCO v2 larger
than v3 larger than before as expected by

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hydro that in proton proton collisions,
this The v2 was measured with different

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techniques in order to reduce the
influence of non flow and actually, it was

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measured to be different from from zero.
So,

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we have v2

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in in small systems and the higher that
there we go in multiplicity at some point

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there is a drift in in v2 from heavy ion
collisions when eccentricity starts to hit

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in So, when Esther says that starts to
play a role, the v2 in large collision

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systems start to be larger than in small
collision systems where, of course, you

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don't have a very big factor in
eccentricities in the initial system. Then

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if we measure if we look at v3 and v4,
which are more sensible to part on density

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fluctuations in the initial system, then
you can see that actually, the comparison

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between the lead lead and Pipi and V lab
is, is much better in the common multiplex

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to regions. It's important to say that
normal that up to now can clearly

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00:23:31,890 --> 00:23:38,280
quantitatively describe the data over the
food multiplicity range nor hydro, not

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even, for example, PTO systems. Now,
talking about let's say collective

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phenomena. It's also very interesting to
study magnetic field effects. As you know,

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in semi central collisions in heavy ions
you have extreme magnetic fields which are

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generated by the spectrum nucleons which
actually quickly decay, but the

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but of course is conserved

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which which means that if you have a
system of free patterns are not free, but

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let's say of atoms of quarks and gluons
interacting in the system, you can develop

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some spin momentum bearing which basically
turns out to have an effect on the spin

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matrix for for example vector
measurements. So, some some values of the

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spin matrix like overall 00 can be
measured which correspond to third

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component of the spin equal to zero with
respect to our given direction. And in

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this case, the relevant direction is the
normal to the event plane because indirect

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is the direction where the B initially is
pointing. And actually this this

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00:24:57,899 --> 00:25:02,699
measurement from the artist collaboration
shows For vector meson k star, you have an

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00:25:02,699 --> 00:25:08,039
effect going lower than the one third
value which would be no polarization,

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which you observe only in heavy ion
collisions and not in proton proton

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collisions, and which you don't observe as
a cross check for zero spin particles like

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zero short. So this is very interesting
because it's consistent with the attorney

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00:25:23,309 --> 00:25:28,289
ization through recombination of Q bar
from the Q GP since you see if you have a

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polarized plasma, this translates into
polarize of polarization or vector

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methods. Now, in the last part of the
talk, I will not go along in the

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00:25:39,029 --> 00:25:43,619
discussion since this was pretty much
covered by wicked at the beginning, but we

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00:25:43,619 --> 00:25:49,379
can try to quantify one minute left. Yes,
very, very good. Thank you very much. You

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00:25:49,379 --> 00:25:56,099
can quantify the characteristic of the
acuity system in heavy ions Bye bye, Asian

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fitting many observables from the
experiments from this specific work from

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00:26:02,219 --> 00:26:08,189
Alice and CMS, for example yields average
bt average speedy fluctuation, v2, v3 and

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00:26:08,189 --> 00:26:13,349
v4. I don't go into details of the model.
Basically, it's a parameterization of many

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of the of the important characteristics of
the system, also initial conditions, and

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then you can try to have posterior
probabilities of this. Below deliverables.

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Yes. Can you hear me?

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Yes. Yes.

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Can anybody hear me?

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If you can, okay.

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Okay, so, No, why? No theory. Well, I'm
basically at the end of my talk, I want to

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just to underline something that was
already covered by Wilker that actually up

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to the 10% level, there is a very good
agreement of this only comprehensive model

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00:27:00,000 --> 00:27:07,020
With with the observation from Alison CMS,
and that you can actually measure for

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00:27:07,020 --> 00:27:12,180
example, the temperature or evolution of
the shear viscosity over entropy density

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00:27:12,210 --> 00:27:18,660
which turns out to be very near to the ADF
CFT lower limit to one over four pine and

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00:27:18,660 --> 00:27:22,710
natural units and which has a mild
dependence of the temperature and compared

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00:27:22,710 --> 00:27:28,140
to any kind of other known fluid in
nature, this is the one which is the

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00:27:28,140 --> 00:27:33,540
nearest to the almost perfect fluid
condition. So, coming to the conclusions I

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00:27:33,540 --> 00:27:38,580
hope I convinced you the soft probes in
IBM collisions allow to characterize the

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00:27:38,580 --> 00:27:42,870
medium with precision. It's a quarterback
confined caramelized medium with an eight

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00:27:42,870 --> 00:27:50,160
arise which is slightly okay or slightly
lower than 0.2 and which is mildly

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00:27:50,160 --> 00:27:55,560
dependent on T on the temperature of the
system. And this system undergoes chemical

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00:27:55,590 --> 00:28:03,810
result at a temperature which is between
150 or 100 and 160 bV and that

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00:28:03,810 --> 00:28:08,070
nucleosynthesis actually from large medium
is consistent with thermal production

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00:28:08,430 --> 00:28:13,050
looking at small colliding system so, I
think that I convinced you that it's they

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00:28:13,050 --> 00:28:16,440
are properly article to a deeper
understanding of the cutiepie phenomenon

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00:28:17,310 --> 00:28:22,860
that hydro chemistry and collectivity at
higher multiplicity in proton proton

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00:28:22,860 --> 00:28:27,060
collisions do match what observed in a
collisions when we look at variables which

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00:28:27,060 --> 00:28:32,790
are not strongly connected to the
collision geometry. And the description of

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00:28:32,790 --> 00:28:37,200
this observation is more systems is very
challenging for any theoretical models.

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So, it says thank you very much. And if
you want to have private discussion, I

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00:28:43,170 --> 00:28:50,430
will be for roughly half an hour in this
zoom. Thank you. Thank you, Olivia. Sorry

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00:28:50,430 --> 00:28:54,090
I stuck. So, we'll have time for

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00:28:55,680 --> 00:28:57,030
your question questions. Please.

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00:28:58,650 --> 00:28:59,370
Shut up.

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00:29:05,940 --> 00:29:06,660
Go

324
00:29:10,500 --> 00:29:13,290
sorry. No, I didn't raise my hand.

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00:29:17,640 --> 00:29:19,080
At least not willingly.

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00:29:21,570 --> 00:29:23,850
Sorry. Anyway, buddy. Nice talk