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ELEMENTARY particles, STRANGE MATTER AND STARSSTRANGERS

I leaves

It has been observed that the protons and the neutrons are presented so much in

scarce portions of matter (nuclei of the diverse chemical elements) like in enormousattachs (stars of neutrons). Among these nuclei (of sizes of the order of meters) and thestars of neutrons (gigantic nuclei of 10 km of radio), an area lacking all type of nuclearmatter extends. It has been speculated that that nuclear desert could be occupied byexotic forms of matter, even not discovered that differ of the ordinary matter.

With more property, the Standard Pattern of the fundamental particles that describesthe physical phenomenons consistently, is not opposed to the existence in new matterways able to fill that desert. For that reason, many physiques are developing investigation

projects in different institutes (as the National Laboratory of Brookhaven), tendientes hasto detect that type of nuclear matter that, in principle, one of the disconcertingcosmological enigmas could explain: 90% of the matter faltante in the universe

observable.

1. Elementary particles and the Standard Pattern

All the phenomenons of our Universe, from the atomic nuclei to the galaxies,they can be descriptos in terms of elementary particles (you leave minimum ofmatter without structure it interns neither apparent radio) and you force orinteractions among this particles.

At the present time they know each other four fundamental forces: gravitational,electromagnetic, weak and strong.

The gravitational force has universal character since one manifests among all the

particles with mass. It is the weakest in the forces but, to the being always attractive andof reach infinite, it allows, for example that the planets rotate around the Sun or that thestars are bound constituting the galaxies. At microscopic level she/he doesn't haveinfluence, I save to very high energy.

The electromagnetic force acts on the particles that possess electric load.. It can beattractive or repellent, according to the type of load setting in game. It is more intensethan the weak force but less than the strong force. Their reach is infinite and, whenallowing that the electrons are bound to the nuclei, it is responsible for the existence ofthe atoms. Also this associated to the the magnetic phenomenons. In 1863, James C.Maxwell was able to unify the electricity and the magnetism in its electromagnetictheory.

The weak force was discovered by Madame Curie when trying to explain thedisintegration radio-active denominated beta. It is more intense than the gravitationalforce and she/he has a very short reach. It carries out an important list in the productionof energy of the Sun and it is the causing of the explosion of the supernovas.

The strong force maintains united the protons and neutrons in the atomic nuclei. It isthe most intense but of short reach, reason why it can not be detected directly to levelmacroscpico. To her the nuclear fission is owed that allows the liberation of energy ofan atomic bomb, and the nuclear coalition, the source of the stars' energy.

The compared intensity and the reach of the four fundamental forces, they areshown in the Chart 1.

It FORCES INTENSITY REACHSTRONGWEAK

1 cmcm

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ELECTROMAGNETICGRAVITATIONAL

1010

102

1038

infiniteinfinite

Chart 1. You force fundamental of the universe

The particles accepted today for the physics they are of two types: the constituent ofthe matter or elementary and the messengers. The elementary particles belong to thefamily of the fermiones, they are particles with spin semientero (1/2) and they obey at the

beginning of exclusion of Pauli (two particles of the same type can not have the samequantum state or energy level").

The particles messengers (or middlemen) they transmit the force betweenelementary particles or fermiones. See from the quantum theory (the physics of themicrocosms), these particles are the how many of the different fields of force(electromagnetic, gravitatorio,etc.). For example the force between two electrons, she/heassociates to the exchange of a particle messenger, a virtual photon that differs (due totheir ephemeral existence) of the real photons that constitute the light or the radialwaves. The particles messengers belong to the family of the bosones, they possess wholespin (0,1,2) and they don't obey at the beginning of exclusion of Pauli (they aregregarious particles). (The spin of an elementary particle is a property of the same onethat has certain analogy with the rotation of a body in lathe of its axis).

To each particle it corresponds him an antipartcula, with the same mass but withopposed electric load. This way, the antipartcula of the electron (with load negative) it isthe antielectrn or positrn (with positive load). The particles messengers coincide withtheir antipartculas.

We will describe, now, the elements of the Standard Pattern. In this model theelementary particles or fermiones are of two types: the leptones and the quarks.

The leptones (of the Greek, small) that know each other they are six, presentingloaded and neuter varieties. The loaded leptones is sensitive to the electromagnetic andweak forces, the neuter ones to the weak force. The better known leptn is the electron(with arbitrary electric load similar to -1). Other leptones is the mun and the taun, withthe same load that the electron, and the neutrinos, without load and worthless or nullmass. Each loaded leptn has associate a neutrino.

The quarks (of German, excess), introduced by Gell-Mann and Zweig in 1963, theyare presented in six different varieties or flavors: up, below, I miss, charmed, bottom andsummit; they are represented with the letters u,d,s,c,b and t (of English: up, down,strange, charm, bottom and top). Also, each quark possesses one of the three " load "types (different from the electric one) or color, designated arbitrarily as red, green and

blue (R,G and B). On the other hand, the electric load of the quarks is fractional (-1/3 or+2/3 according to the flavor).

The leptones and the quarks sae contain in three generations (I, II and III). Eachone of them is integrated by two quarks, a loaded leptn and their associate neutrino.The daily matter consists on associations of the four particles of the generation I. Thetwo following generations, except for the neutrinos, are extremely unstable particles thatyou/they only appear in the laboratories of high energy.

The properties of the leptones and the quarks can it turns in the Chart 2.

QUARKS MASS ItLOADS

LEPTONES MASS ItLOADS

Iup, or

below, d0.30.3

+2/3-1/3

electron,neutrino,

0.00050?

-10

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II

I love, cI miss, s

1.50.5

+2/3-1/3

mun,neutrino,

0.106

0?-10

III

summit, t

bottom, b1754.5

+2/3-1/3

taun,neutrino,

1.70?

-10

Chart 2. Constituent of the matter (fermiones)(the masses are expressed in GeV. 1GeV are the energy that she/he acquires an electronto the subjected being to a difference of potential of 1000 million volts)

The particles messengers (bosones) associated to the fundamental forces they are:the photon to the electromagnetic force, the glun (of the English glue: line of hitting) tothe strong force and the vectorial bosones, and to the weak force (to see Chart 3). Thegravitn (of null, hypothetical mass) she/he associates to the gravitational field.

We had seen that the quarks possessed color load. It can be demonstrated that areneeded to transmit the strong force eight gluones, some of which possess color load. Thequarks is also sensitive to the weak force. But while the strong force (through the

gluones) it changes the color of the quarks, the weak force (through the vectorialbosones) it changes their flavor.

VECTORIAL BOSONES

W+ W

Z0

Photon GLUNg

MASS 80 80 91 0 0It LOADS +1 -1 0 0 0

It FORCES Weak Weak WeakElectro -magnetic Strong

Chart 3. Messengers of the force (bosones)(the masses are expressed in GeV)

2. Hadrones and strange matter

The particles constituted by quarks, sensitive to the strong force, they aredenominated hadrones (of the Greek hadros: robust). They can be of two classes: the

bariones (of the Greek, heavy) formed by three quarks types (each one with a differentcolor) and the consistent taverns in a quark and an antiquark (with a color and theirrespective anticolor). The combination of colors in the hadrn should always give theneuter color. Bariones examples are: the proton, composed up by two quarks and one

below, and the neutron for two quarks below and one up. These two bariones is stableand they constitute the ordinary matter. A typical tavern is the positive pin, formed up

by a quark and an antiquark below. Other hadrones is shown in the Chart 4.

TYPE NAME COMBINATIONSDE QUAKS

BARIONES proton pneutron n

positive sigma

lambdaOmega

uududduus

yousss

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TAVERNS positive pinpositive kannegative kanOf neuter

ororsc

Chart 4. Typical Hadrones(the symbol ~ it means anti)

The hadrones can be descriptos like bags where the quarks can move with certainfreedom, but without ending up never escaping (it is said that they are permanentlyconfined). Inside the bag, the weak force changes the identity of the quarks. This forcecan transform the quark d (below) in the quark or (up). A neutron (udd) she/he becomesa proton (uud), because to that the weak force changes the identity of one of its quarks din a quark or. In this process it is also generated an electron and an antineutrino. Theweak force can also change a quark s (I miss) in a quark d. This property explains theuncertainty of the particles that you/they contain strange quarks (denominated strange

particles), as the bariones sigma () and lambda (), and the taverns and.

Do let us analyze, now, the following possibility: do stable bags composed exist formore than three quarks? In the ordinary matter this situation is not presented. Indeed, toweigh that the protons and neutrons are bound constituting the nuclei, the quarks doesn'tgroup in an only bag multiquark, but rather they remain forming bags of three quarks(bags of protons [uud] and bags of neutrons [udd]). Now then, you can surmise that ifstrange quarks is added up to the quarks combinations and below, bags could beobtained of more than three quarks. To the combinations of a number approximatelysimilar of quarks up, quarks below and strange quarks contained in oneself bag, itdenominates it to him matter of strange quarks or strange matter (to see Fig.1). In 1971,A. R.Bodmer surmised that these attachs of strange quarks could constitute the densestable nuclei inside the stars.

ords

Matter nuclear strange Matter

Fig 1. Example of nuclear matter (deuterio nucleus) and bag of strange matter

In 1984, E. Witten suggested that the mass faltante in the universe would becomposed by matter of strange quarks whose origin goes back to the first instants of theBig - Bang. In that stage they were formed extremely compressed pellets of matter ofstrange quarks and with diameters of up to 10 centimeters. In the same year, E. Farhi andR. Jaffe, of the Institute of Technology of Massachusetts (MIT), using the pattern for thecalculation of the mass of the hadrones, they determined that portions of much morestrange matter that the predichas for Witten (called strangelets) they could be absolutelystable. Of being proven this, the strange matter would be the candidate to fill the existentempty space between the nuclei of normal matter and the stars of neutrons (nuclear

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desert). Is it even necessary to be formulated the following question: is the starsultradensas constituted of matter neutrnica or strange matter?.

In the next article we will analyze the enormous bags of strange matter: the strangestars, I eat the intense search of this new matter type likewise, in cosmology, geophysicsand in the laboratories of high energy. -

Rosario, July de1998 31. -

Luis P. Neira

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