HADRONIC PHYSICS IN SPAIN

NUPECC meeting

Madrid (Spain), March 7, 2008

Topics: Chiral Perturbation TheoryQCD Sum RulesEffective Field TheoryExotic HadronsHadron Properties from LatticeExperimental Results and Future PerspectivesHadronic Distribution Amplitudes

Spectroscopy of light and heavy quark mesonsBaryonsQuarkoniaGlueballs, hybrids and multiquarksPhenomenological modelsEffective lagrangiansQCD on the latticeHadrons in matterHeavy ion collisionsFuture facilities

Define Hadronic physics, 1 o 2 slides

Theory

Experiment

We fit our 12 free parameters to 370 data points andtheir reproduction from ππ threshold up to 2 GeV is fairas shown in Fig.1. The width of the band represents oursystematic uncertainties at the level of two standard deviations.The fitted data are from left to right and topto bottom, ππ I = 0 S-wave phase shifts δ00, the elasticityparameter η00 = |S11|, the I = 0 S-wave ππ → K ¯Kphase shifts δ1,2, |S1,2|, the S-wave contribution to theππ → ηη event distribution and the event distributionfor ππ → ηη′. The last two panels corresponds to thephase (φ) and modulus (A) of the K−π+ → K−π+ amplitude from the LASS data. Comparedwith other works we determine the interaction kernelsfrom standard chiral Lagrangians, avoiding ad-hoc parameterizations.

  Departamento de Física de Partículas, University of Santiago de Compostela , Santiago de Compostela, Spain

  D. Belver     P. Cabanelas     E. Castro     J. A. Garzón     Instituto de Física Corpuscular, Universidad de Valencia-CSIC , Valencia, Spain

  J. Díaz     A. Gil  

The investigation of hadron properties inside nuclear matter at normal and high densities and temperatures is one of the main goals of current nuclear physics studies. Hadron induced reactions on heavy nuclei (e.g. Au, Pb) are the proper tool to probe particle properties in long-living ground state nuclear matter. Heavy ion collisions at energies of 1-2 AGeV can be used to create a reaction region of increased density for as long as 10 fm/c. Under these conditions, considerable modifications of basic hadron properties (masses, decay widths, etc.) are expected and probably can be verified for the first time experimentally by high resolution lepton pair decay measurements.

In order to investigate this phenomenon, the electron-positron pair spectrometer HADES was set up, and is in operation, at GSI by an international collaboration of 17 institutions from 9 European countries.

Excited Glue(Glueballs and Hybrids)

Charm in Nuclei

Charmonium

Hypernuclei

D- and DS-Physics

Other Topics

                

The ALICE Collaboration is building a dedicated heavy-ion detector to exploit the unique physics potential of nucleus-nucleus interactions at LHC energies. Our aim is to study the physics of strongly interacting matter at extreme energy densities, where the formation of a new phase of matter, the quark-gluon plasma, is expected. The existence of such a phase and its properties are key issues in QCD for the understanding of confinement and of chiral-symmetry restoration. For this purpose, we intend to carry out a comprehensive study of the hadrons, electrons, muons and photons produced in the collision of heavy nuclei. Alice will also study proton-proton collisions both as a comparison with lead-lead collisions in physics areas where Alice is competitive with other LHC experiments

SPAIN, MADRID, CIEMAT; TL&CP: Pedro LADRON DE GUEVARASPAIN, SANTIAGO DE COMPOSTELA, UNIVERSIDAD DE SANTIAGO DE COMPOSTELA; TL&CP: Carlos PAJARES

in-medium modifications of hadrons in dense matter. indications of the deconfinement phase transition at high baryon densities. the critical point providing direct evidence for a phase boundary. exotic states of matter such as condensates of strange particles. The approach of the CBM experiment towards these goals is to measure simultaneously observables which are sensitive to high density effects and phase transitions (see figure 2 for an illustration). In particular, the research program is focused on the investigation of:short-lived light vector mesons (e.g. the ρ-meson) which decay into electron-positron pairs. These penetrating probes carry undistorted information from the dense fireball. strange particles, in particular baryons (anti-baryons) containing more than one strange (anti-strange) quark, so called multistrange hyperons (Λ, Ξ, Ω). mesons containing charm or anti-charm quarks (D, J/Ψ). collective flow of all observed particles. event-by-event fluctuations.

Resonance physics in chiral unitary approaches

A. Ramos (University of Barcelona)

Workshop on the physics of excited nucleons (NSTAR 2007)5-8 September 2007

Bonn, Germany

Chiral unitary model

The (1405) and its two-pole nature

Other sectors: eg S=-2 resonances

Heavy flavored baryon resonances

Outline:

K N scattering: a lively topic

K N scattering in the I=0 channel is dominated by the presence of the (1405), located only 27 MeV below the K N threshold

Already in the late sixties, Dalitz, Wong and Rajasekaran [Phys. Rev. 153 (1967) 1617] obtained the (1405) as a KN quasi-bound state in a potential model (Scrhoedinger equation).

The study of KN scattering has been revisited more recently from the modern view of chiral Lagrangians. However, the presence of a resonance makes PT not applicable non-perturbative techniques implementing unitarization in coupled channels are mandatory!

1. Build a transition potential V from the meson-baryon Lagrangian at lowest order

2. Unitarization: N/D methodequivalent to Bethe-Salpeter coupled-channel equations with on-shell amplitudes

Mj

BjBi

Vij = Mi

s-wave

M B coupled channels for S=-1:

Pioneer work: N.Kaiser,P.B.Siegel,W.Weise, Nucl.Phys.A594 (1995) 325 omitted

next-to-leading order: L2

KKN1255 1331 1435 1663 1741 1814 (MeV)

Chiral Unitary Model:

Tij = Vij + Vil GlTlj

= +

Loop function

Cut-off regularization (as in E. Oset and A. Ramos, Nucl. Phys. A635 (1998) 99):

Dimensional regularization (as in J.A. Oller and U.G. Meissner, Phys. Lett. B500 (2001) 263 ):

subtraction constants of “natural size” (equivalent to cut-off ~ 1 GeV)

K-p low energy scattering properties and the (1405)

adjusted to reproduce branching ratios:

2.32

0.627

0.213

E. Oset and A. Ramos, NPA635 (1998) 99

Invariant mass distribution

Y channels are necessary to: obtain a good description of the threshold branching ratios (especially ) preserve SU(3) symmetry

(1.04 without )

=630 MeV (f=1.15f)

Elastic and inelastic cross sections

p-waves also included(D.Jido, E.Oset, A.Ramos, PRC66 (2002) 055203)

+

Total cross sections

Differential cross sections

Since the pioneering work of Kaiser, Siegel and Weise [Nucl. Phys. A594 (1995) 325] many other chiral coupled channel models have been developed.

E. Oset and A. Ramos, Nucl. Phys. A635 (1998) 99J.A. Oller and U.G. Meissner, Phys. Lett. B500 (2001) 263M.F.M. Lutz, E.E. Kolomeitsev, Nucl. Phys. A700 (2002) 193C.Garcia-Recio et al., Phys. Rev. D (2003) 07009

M.F.M. Lutz, E.E. Kolomeitsev, Nucl. Phys. A700 (2002) 193

more channels,next-to-leading order,Born terms beyond WT (s-channel, u-channel),Fits including new data…

B.Borasoy, R. Nissler, and W. Weise, Phys. Rev. Lett. 94, 213401 (2005); Eur. Phys. J. A25, 79 (2005) J.A. Oller, J. Prades, and M. Verbeni, Phys. Rev. Lett. 95, 172502 (2005)J. A.Oller, Eur. Phys. J. A28, 63 (2006)B. Borasoy, U. G. Meissner and R. Nissler, Phys. Rev. C74, 055201 (2006).

The two-pole structure of the (1405)

The meson-baryon states built from the 0- pseudoscalar meson octet and the1/2+ baryon octet can be classified into SU(3) multiplets:

8 X 8 = 1 + 8s + 8a + 10 + 10 + 27 meson X baryon

In the SU(3) basis:

attractive

Taking common baryon and meson masses (Mi~M0, mi~m0) in both Vij and Gl

one obtains a SU(3) symmetric Tij

a singlet (1) and two degenerate octets (8s,8a) of Jp=1/2- bound states appear!

1 8a 8s 10 10 27

D. Jido, J.A. Oller, E.Oset, A.Ramos, U.G. Meissner, Nucl. Phys. A725 (2003) 181C. Garcia-Recio, J.Nieves, M.Lutz, Phys. Lett. B582 (2004) 49

Breaking SU(3) gradually Mi(x) = M0 + x (Mi-M0)up to the physical masses: m2

i(x) = m20 + x (m2

i-m20)

x=0.(0.1)1 ai(x) = a0 + x (ai-a0)

M0 = 1151 MeVm0 = 368 MeVa0 = -2.148

S=-1 sector

In I=0, the evolved octet and the evolved singlet appear very nearby:

The nominal (1405) is the reflection of two poles of the T-matrix !

s

|T|2pcm

T selects preferentiallythe lower energy(wider) pole

TKN selects preferentiallythe higher energy (narrower) pole

The properties of the (1405) will depend on which amplitude initiates the reaction!

zR 1390 - 66i 1426 - 16i 1680 - 20i

(I=0) |gi| |gi| |gi|

2.9 1.5 0.27

2.1 2.7 0.77

0.77 1.4 1.1

0.61 0.35 3.6

S=-1 poles and couplings to physical states with I=0

Experimental evidence

-pK0

D.W.Thomas et al.Nucl. Phys. B56, 15 (1973)

K-p

S. Prakhov et al.,Phys.Rev. C70,034605 (2004)

confirmed by models!

where:

T.Hyodo, et al, Phys. Rev. C68 (2003) 065203

+

-pK0

The N*(1710) mechanismstresses the role of T

The chiral termsstress the roleof TKN

V. K. Magas, E. Oset and A. Ramos,Phys. Rev. Lett. 95, 052301 (2005)

K-p

MI ~ 1420 MeV

dominated by the amplitude TKN

Other sectors

JP=1/2-

S=0 N*(1535)N. Kaiser, P.B. Siegel, W. Weise, Phys. Lett. B362 (1995) 23J.C. Nacher et al., Nucl. Phys. A678 (2000) 187T. Inoue, E. Oset, M.J. Vicente-Vacas, Phys. Rev. C65 (2002) 035204J. Nieves and E. Ruiz Arriola, Phys. Rev. D64 (2001) 116008M.F.M. Lutz, E.E. Kolomeitsev, Nucl. Phys. A730 (2004) 110 …

S=-2 (1620), (1690)A. Ramos, E. Oset, C. Bennhold, Phys. Rev. Lett. 89 (2002) 252001C. Garcia-Recio, J.Nieves, M.Lutz, Phys. Lett. B582 (2004) 49

JP=3/2-

(Interaction of the 0- meson octet with the 3/2+ baryon decuplet)

(1700),(1520),(1670),(1820)

E.E. Kolomeitsev, M.F.M. Lutz, Phys. Lett. B585 (2004) 243S. Sarkar, E. Oset, M.J. Vicente-Vacas, Phys. Rev. C72 (2005) 015206L. Roca, S. Sarkar, V.K. Magas and E. Oset, Phys. Rev. C73 (2006) 045208M. Döring, E. Oset, D. Strottman, Phys. Rev. C73 (2006) 045209M. Döring, E. Oset, D. Strottman, Phys. Lett. B639 (2006) 59

Experimental situation:

p-wave: (1530)**** I=1/2 JP=3/2+

s-wave: (1620)*, (1690)*** I=1/2 JP: not measured

(1620) = 20 – 50 MeV (into states) (seen recently at CLAS in the p - K+ K- () reaction)

(1690) = 10 – 50 MeV (into states) 1 : 1/3 : 1/10

We looked for dynamical resonances in the S=-2 sector, by solving the unitarycoupled channel problem with the states:

zR 1605 - 65i

(I=1/2) |gi|

2.4

2.6

0.96

0.48

Taking:a=-3.1a=-1.0a=-2.0a=-2.0

We identify this resonance with the(1620)*

JP=1/2- can be assigned!

A. Ramos, E. Oset, C. Bennhold,Phys. Rev. Lett. 89 (2002) 252001

S=-2

(of natural size)

invariant mass distribution

threshold: 1611 MeV

~50 MeV

The “apparent” width (~50 MeV) is much smaller than the actual width at the pole position (~130 MeV)

(Flatté effect: resonance just below a threshold to which the resonance couples strongly)

Heavy flavoured baryon resonances

In the charm sector we find a resonance. the c(2593) (udc), that bears a strong ressemblance to the (1405) (uds) in KN dynamics

Can we generate the c(2593) dynamically from DN dynamics?

The DN interaction is intimately connected to the properties of the D-meson in a nuclear medium

It is produced in pairs (D+,D-)

• in heavy ion experiments:

• or antiproton anhilation experiments (PANDA at FAIR) on protons and nuclei:

Understanding the interaction of charmed mesons in a hadronic medium is an important issue:

There are hints that a D Dbar meson-pair could feel attraction: an open charm enhancement has been observed in nucleus-nucleus collisions by the NA50 Collaboration

If the mass of the D (and Dbar) mesons gets reduced appreciably in the medium (cold or hot), this would provide a conventional hadronic physics explanation to explain J/ supression (attributed to be a signal for the formation of a Quark-Gluon Plasma)

QCD sum rule (QCDSR)

The in-medium mass shift is obtained in the low density approximation from the product of the mass of the charmed quark (mc) and the light meson q-qbar condensate:

A. Hayashigashi, Phys. Let. B487, 96 (2000)

P. Morath, W. Weise, S.H. Lee, 17 Autumn school on QCD, Lisbon 1999 (World Scientific, SIngapore, 2001) 2001

Nuclear Mean Field approach (NMFA)

D-meson self-energy is calculated by supplementing the contribution of the free meson-baryon lagrangian:

with additional terms describing the interaction of the D with mean scalar () and vector () density-dependent meson fields

A.Mishra, E.L. Brakovskaya, J. Schaffner-Bielich, S. Schramm, and H. Stoecker, Phys. Rev. C 70, 044904 (2004)

Variety of results, depending on ingredients of the model and its parameters:

Quark Meson Coupling approach

Hadron interactions mediated by the exchange of scalar-isoscalar ( and vector ( and ) medium modified mesons among the light constituent quarks.

A.Sibirtsev, K.Tsushima, and A.W.Thomas, Eur. Phys. J. A6, 351 (1999)

These models predict a substantial reduction of the D-meson mass to which a scalar-isoscalar attraction appears to play an important role

However, the full dynamics of the DN interaction (e.g. coupled channels) might be crucial (due to the presence of the c(2593) (udc)

L. Tolós, J. Schaffner-Bielich, and A. Mishra,Phys. Rev.C 70, 025203 (2004) (T=0 MeV)L. Tolós, J. Schaffner-Bielich, and H. Stöcker,Phys. Lett. B635, 85 (2006) (finite T)

Channels for C=1, S=0

M.F.M.Lutz and E.E.Kolomeitsev, Nucl. Phys. A730, 110 (2004)

Earlier attempts of coupled-channel calculations of the DN amplitude

Exploits the similarity between (1495) and c(2593):s replaced by c in a SU(3) chiral invariant model (only channels with non-strange hadrons)The c(2593) is generated as a DN s-wave molecular state having a width of 3 MeV

Scattering of Goldstone bosons (,K, ) off ground state charmed baryons (c, c …). Proper symmetries respected but no DN, DsY channelsI=0, C=1 resonance found at 2650 MeV that couples strongly to c (very large width ~ 80 MeV)

Ideally: include all channels extend chiral MB-MB lagrangian to SU(4)

However, c quark is very heavy mc ~1.4 GeV !

J.Hofmann and M.F.M.Lutz, Nucl. Phys. A763, 90 (2005)

t-channel exchange of vector mesons: V

universal vector coupling constant

SU(4) at the vertices:

chiral symmetry in the light sector imposed

SU(4) symmetry broken by the use of physical masses. In particular:

DN amplitudes

I=0 I=1

DN DN

(dimensional regularization)

In-medium amplitude

contains:

Self-consistent dressing of D-meson

Pauli blocking on intermediate nucleons

M.F.M.Lutz, and C.L.Korpa, Phys. Lett. B 633,43 (2006)

cannot be regularized via DR use a cut-off But, the in medium

free amplitude T must be also determined with a cut-off

We obtain T with a loop function regularized with a cut-off [adjusted to reproduce c(2593)]

T. Mizutani, A. Ramos, Phys. Rev. C74, 065201 (2006)

We include an additional scalar-isoscalar interaction ( term)

(from QCDSR)

Model A:

Model B:

I=0 I=1

DN amplitudes(with cut-off regularization)

R. Mizuk et al. [Belle Collaboration]Phys.Rev.Lett.94, 122002(2005)c(2800), ~60 MeV

D-meson self-energy and spectral density and 2

L. Tolos, A. Ramos and T. Mizutani, in preparation

quasiparticle peak

Conclusions

In the heavy sector, we have studied the DN interaction in coupled channels from a model inspired

on the work of Hofmann and Lutz, with some modifications: a supplementary scalar-isoscalar interaction is introduced momentum cut-off regularization more consistent than DR in view of its application to

meson-baryon scattering in the medium

The model generates the c(2595) in I=0, together with another resonancewith I=1consistent with the observed c(2800)

Combining chiral dynamics with a non-perturbative unitarization technique, one can extend the range of applicability of the chiral lagrangian to study resonances.

In the light sector, the 1405 provides an excellent example of a dynamically generated resonance.

There are two I=0 poles building up the nominal 1405These two resonances couple differently to and states and, as a consequence, the “properties” of the 1405 (mass and width) will depend on the particular reaction employed to produce it.