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Bologna 6 Nov. 2015 Luciano MAIANI. Antimatter

The Biggest Jump (Antimatter today)

Luciano Maiani Sapienza Universita’ di Roma and INFN

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20 years ago…What happened since?

Antimatter – in the Universe – in the Lab – messenger of Dark Matter – reference candle for multi

quark states

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from the foreword of 1995 (LM, R. A Ricci)

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Fifty

The more after the success of the Standard Theory, the Higgs boson, etc.

Bologna 6 Nov. 2015 Luciano MAIANI. Antimatter 4

done!


Antimatter in the LHC era

The ALICE experiment at CERN makes precise comparison of light nuclei and antinuclei (17 August 2015) The ALICE experiment at the Large Hadron Collider (LHC) at CERN has made a precise measurement of the difference between ratios of the mass and electric charge of light nuclei and antinuclei. The result confirms a fundamental symmetry of nature to an unprecedented precision for light nuclei. The measurements are based on the ALICE experiment’s abilities to track and identify particles produced in high-energy heavy-ion collisions at the LHC. The ALICE collaboration has measured the difference between mass-to-charge ratios for deuterons and antideuterons, as well as for helium-3 nuclei and antihelium-3 nuclei.

Measurements at CERN, most recently by the BASE experiment, have already compared the same properties of protons and antiprotons to high precision.

The study by ALICE takes this research further as it probes the possibility of subtle differences between the way that protons and neutrons bind together in nuclei compared with how their antiparticle counterparts form antinuclei. The new result, which comes exactly 50 years after the discovery of the antideuteron at CERN and in the US, improves on existing measurements by a factor of 10-100.

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1. ANTIMATTER

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Alice through the Looking Glass

How would you like to live in Looking-glass House, Kitty? I wonder if they'd give you milk in there? Perhaps Looking-glass milk isn't good to drink --

The sign of the charge is conventional reflecting all charges does not change Maxwell’s equations but in classical physics there is no way to confront our world with the looking glass world


• Dirac: a symmetry between electrons and electron holes makes so that they have opposite charge and the same mass

• to all effects, the hole is a “reflected image of the electron: it is an “anti-electron”

• same should hold for protons, neutrons….atoms

• world and anti world exist at the same time

• and we can compare them


2. ANTIMATTER IN THE UNIVERSE

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On the Earth a positron annihilates quickly with the surrounding electrons (e.g. in the Positron Electron Tomography-PET) Dirac: but what about distant stars? or the universe at large? If we accept the view of complete symmetry between positive and negative electric charge so far as concerns the fundamental laws of Nature, we must regard it rather as an accident that the Earth (and presumably the whole solar system), contains a preponderance of negative electrons and positive protons. It is quite possible that for some of the stars it is the other way about, these stars being built up mainly of positrons and negative protons. In fact, there may be half the stars of each kind. The two kinds of stars would both show exactly the same spectra, and there would be no way of distinguishing them by present astronomical methods (P. A. M. Dirac, Nobel Lecture, 1933)

Are there Antimatter Islands in the Universe? 20 years ago we had doubts Satellite experiments (Pamela, AMS) made to measure the flux of anti He4 in cosmic rays


AMS-01/02

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• assume:xHe = (

Dus

Da.m.

)

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Dus ⇠ 30kpc (galaxy)

• one finds:

xHe = 1 · 10�6(AMS� 01, Pamela)

Da.m. ⇠ 30 Mpc (Virgo Cluster)

xHe = 1 · 10�9(AMS� 02, future)

Da.m. ⇠ 1000 Mpc (visible Universe)

• The best limits on antinuclei in cosmic rays have been obtained with satellite born magnetic spectrometers: Pamela and AMS-01/AMS-02 on the International Space Platform

• xHe=Flux(Anti Helium/Flux(Helium) the preferred signal: far anti-galaxies would it cosmic antiHelium nuclei much like our galaxy emits cosmic ray Helium nuclei

• upper bounds on xHe give us an della distanza estimate of of an anti-galaxy

Bologna 6 Nov. 2015 L. Maiani. Antimatter

What ALICE found in the looking glass

+ ( )Mirror ??? Not goodchemistry does not fit

( )Mirror +( ) Mirror ??? Not good eitherParity Violation, 1956

For some time it was believed that:

(Anti- ) Mirror + (Anti- ) Mirror

would work in our world (CP symmetry, Salam, Landau…)

3. Antimatter in the Lab

Bologna 6 Nov. 2015 L. Maiani. Antimatter

Until it was discovered that K-mesons behave differently...

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KL (decay products) (anti- decay products) Mirror

(Cronin, Fitch et al. ,1964) ≠

This may happen in two ways:

(i): KL (anti- K L ) Mirror parameter ε | ε | 2 10−3

(ii): (anti- ) Mirror parameter ε’

In (ii) the weak forces are responsible of asymmetry: direct CP violation ..this is what we see on Earth...and in the Galaxy:

≠ ≅

≠


Charge conjugation x Parity x Time reversal does work!(for the time being…)

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The DAFNE collider, LNF, Frascati

The Antiproton Decelerator, CERN

BASE@AD

CLOE @DAFNE

X p K0 e µ

|m(X)�m(X̄)|m(X) 10�10 10�18 10�8

|µ(X)+µ(X̄)|µ(X) 10�12 10�8


4. Antimatter from annihilation or decay of Dark Matter particles (WIMPS)

• antiprotons are produced in cosmic ray collisions against interstellar gas, with decreasing energy spectrum;

• high energy positrons and antiprotons may arise from the decay of long-lived WIMPs or from annihilation processes of (Majorana) WIMPs

• structures in energy spectrum?

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• anomaly observed in positron spectrum, still of controversial origin: – PAMELA (Italo-Russian) pioneering experiment, clear signal of positron

spectrum rise – AMS (intern. coll. with important italian participation: INFN, ASI) istalled

on the International Space Station, has collected animpressive munte of data, with more recise indications on the rise of positron spectrum, but…., only up to a possible turning point

Mass distribution in the Universe from WMAP


Pamela

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Positron fraction

PAMELA courtesy of P.G. Picozza


S. Ting18 September 2014

S. Ting

R. Battiston

New Results from the Alpha Magnetic Spectrometer

on the International Space Station

Time of Flight SystemMeasures Velocity and Charge of particles

Z=2 Z=6σβ=2% σTime=80ps

σβ=1.2% σTime=48ps

x103

Velocity [Rigidity>20GV]

Eve

nts

Velocity [Rigidity>20GV]

Eve

nts

Plane 4

3, 4

HHe

Li BeB C

NO

FNeNaMg

AlSi

Cl Ar KCa

ScTi VP S

CrFe

Ni

Mn

Zn

Bologna Prof. A. Contin, G. Laurenti, F. Palmonari

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Collision of “ordinary” Cosmic Rays produce e+, p.. Collisions of Dark Matter (neutralinos, χ) will produce additional e+, p, …

The Origin of Dark MatterThe physics objectives of AMS include:

Donato et al., PRL 102, 071301 (2009)

Antiprotons: χ + χ → p + …

Collision of Cosmic Rays

mχ= 1 TeV

Positrons: χ + χ → e+ + …

mχ=800 GeV

Collision of Cosmic Rays

I. Cholis et al., arXiv:0810.5344

mχ=400 GeV

e± energy [GeV]

e+ /(

e+ +

e- )

M. Turner and F. Wilczek, Phys. Rev. D42 (1990) 100118

Positron Flux

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(i)

(iv)

The Positron FracVon

(ii)

(iii)

(v) δ ≤ 0.030

(vi) The expected rate at which it falls

beyond the turning point.

e± energy [GeV]

Posi

tron

frac

tion

Pulsars

Collision of cosmic rays

mχ = 700 GeV275±32 GeV

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5. Light nuclei (antinuclei) as ‘reference candle'

• Recently, the issue has arisen if there are genuine multi quark hadron states (hadrons that can be described as made by colored subconstituents) or only hadron molecules (hadrons that can be described as made by cold singlets constituents).

• Nuclei obviously belong to the second class, being ‘made’ by color singlet protons and neutrons

• but what about objects like the $X(3872)$, a narrow state decaying into J/ Ψ+ρ/ω or DD* (therefore containing a charm-anticharm quark pair) and not foreseen in the charmonium series ? is this a DD* molecule (2nd case) or a diquark-antidiquark state (1st case)?

• Alice has measured the production of light nuclei, deuteron, He3 and hypertriton, H3Λ in relatively high pT bins in Pb-Pb collisions, at sNN = 2.76 TeV

• The cross section of these processes can be used as reference for a discrimination between the above cases.

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•For long, we lived with the simplest paradigm:

•The case had to be revisited, because the lowest lying scalar mesons- f0(980), a0(980), kappa(800) and sigma(600)- do not fit in the picture.

•In 2003 the experiment Belle (Japan) discovered a particle, X(3872), which does not fit into the “charmonium” (charm-anticharm quark) states,

•since then, Belle, BaBar, BES and LHcB have reported many other states that do not fit the charmonium picture, called X (1++) and Y(1--) states.

•In 2007, Belle observed a charged “charmonium”, Z+(4430) → ψ(2S)+ π, that could not be interpreted as molecule, but later Babar suggested it was simply a reflection of K* states. LHCb has confirmed the Z+(4430) while other similar states, Z+(3900) and Z+(4020), have been established.

•Z+→ ψ(2S)( ) + π+( ), hence : tetraquark •The LHCb P+→ p(uud)+J/Ψ(c anti c) hence it has : pentaquark

M. Gell-Mann, A Schematic Model of Baryons and Mesons, PL 8, 214, 1964

mesons = qq̄, baryons = qqq

cc̄

4q + 1q̄

2q + 2q̄ud̄

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Exotic hadrons



options for Color neutral states

8c

8cthe ‘hybrid’ option

quark (heavy or light)

antiquark

gluon

6c

6̄c

8c ...less bound

8c

Models for X Y Z mesons

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X: a loosely bound molecule (R ~10 fm)

1c

1c

a compact `tetraquark’

3̄c

3c

(R=1 fm)

R ⇡ 1p2MDEbind


with q → baryon (e.g. Λ), Y-shape with → scalar meson, H-shape (Rossi &Veneziano, 1980)

[qq]

[qq][q̄q̄]! [qq][q̄q̄] + meson

string topology is more related to Baryon-antiBaryon: if you break the string,

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QCD forces are attractive for diquarks in the configuration [qq’]: color = 3bar, -diquarks make a simple unit to form hadrons (Jaffe & Wilcezck, 2003) - diquarks needs to combine with other colored objects to form a confined object (hadron)

Many states: tetraquarks may have radial and orbital excitations

q[qq]

Meson-meson molecules have a different string topology: - are they bound? - very few states

A. De Rujula, H. Georgi and S. L. Glashow,Phys. Rev. Lett. 38 (1977) 317.

Diquarks or molecules


Replacing one antiquark with a diquark makes new objects

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rule:

meson

baryon tetraquark

baryon

X, Y, Z mesons


A. Esposito, A. Guerrieri, L. Maiani, F. Piccinini, A. Pilloni, A.Polosa and V. Riquer, Phys. Rev. D 92 (2015) 3, 034028

Rescaling from Pb-Pb ALICE cross sections to p-p CMS cross section is done with: Glauber model ( left panel) and blast-wave function ( right panel}) (RAA or RCP =1)

Collective effects in Pb-Pb (e.g.quark-gluon plasma) enhance nuclear cross sections and therefore reduce the cross section rescaled to p-p.


more spectacular results for 2 and 3 substitutions in baryons

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baryon

u

c

ud

u

d

dibaryon ???

pentaquark

u

c

ud

c̄

P+ ! (cc̄) + (uud) = J/ + p

L. Maiani, A. D. Polosa and V. Riquer, PLB 749 (2015) 289

L. Maiani. PentaquarksMCTP-UNACH, Tuxtla Gt, August 13, 2015

.

Geneva, 14 July 2015.

Today, the LHCb experiment at CERN’s Large Hadron Collider has reported the discovery of a class of particles known as pentaquarks. The collaboration has submitted a paper reporting these findings to the journal Physical Review Letters.

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“The pentaquark is not just any new particle,” said LHCb spokesperson Guy Wilkinson. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over fifty years of experimental searches.

Mass of J/ψ–proton combinations from Λb → J/ψ p K- decays. The contributions from the Pc(4380) and Pc(4450) states are indicated. Inset: the mass of J/ψ p combinations for a restricted range of the K-p mass

JP=3/2- JP=5/2+

L. Maiani. PentaquarksMCTP-UNACH, Tuxtla Gt, August 13, 2015

Dibaryon decays

•A dibaryon could decay in several different ways

•By string breaking, into baryon+pentaquark, e.g.:

•By quark rearrangement, into two baryons, e.g.:

•By beta decay of the c quark ( ), lifetime ≈ 10-12 s:

D+c ! p+ ⌃0

c ! p+ ⇤+c + ⇡�

M(D+c ) > 3390 MeV

D+c ! e+⌫e + ⌃� + p, M(D+

c ) > 2135

D+c ! e+⌫e +�� + p, M(D+

c ) > 2170

c ! s(d) + e+ + ⌫e

L. Maiani, A. D. Polosa and V. Riquer, in preparation


Conclusion

• Antideuteron observation in 1965: an important experiment at a critical time

• established CPT for nuclear forces • a very difficult technology, which has found applications in many

fields until today. • Meanwhile, our view of hadrons has changed a lot: quarks,

asymptotic freedom, Standard Theory…. • New hadrons are emerging, maybe a new spectroscopy • high energy production of light nuclei and antinuclei at colliders,

pioneered by Nino’s experiment is a very effective tool to discriminate different models.

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MANY THANKS, NINO!!! AND GOOD ANNIVERSARY

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