3rd RICAP, May 26, 2011 NEVOD-DECOR experiment and evidences of quark-gluon plasma in cosmic rays A.A.Petrukhin for Russian-Italian Collaboration National Research Nuclear University MEPhI, Russia Istituto di Fisica dello Spazio Interplanetario, INAF, Torino, Italy Dipartimento di Fisica Generale dell’ Universita di Torino , Italy Contents 1. New method of EAS investigations. 2. Experimental complex NEVOD-DECOR. 3. Results of muon bundle investigations. 4. Evidences of new physics in CR. 5. Model of QGP production. 6. Possibilities of new model check.

New method of EAS investigations

Methods of EAS investigations Number of electrons Ne (in fact, mixture of charged particles) Number of muons, N Energy deposit of EAS core, Eh Cherenkov radiation flux, FCh Fluorescence radiation flux, Ff Radio emission flux, Fr Local muon density, D - results Muon bundle energy, E - plans New!

Inclined EAS detection (local muon density measurements) Advantages: - practically pure muon component; - large area of showers, which increases with energy.

μ-EAS transverse section VS zenith angle Number of detected EAS depends on: shower array dimensions shower dimensions only

Traditional EAS detection technique (E ~ 1018 eV) ~ 500 m EAS counters (~ 1 m2)

Local muon density spectra detection technique E ~ 1018 eV, θ=80º Muon detector ~ 10 km

Contribution of primary energies at different zenith angles Wide angular interval – very wide range of primary energies !

Experimental complex NEVOD-DECOR

General view of NEVOD-DECOR complex Coordinate-tracking detector DECOR (~115 m2) Cherenkov water detector NEVOD (2000 m3) Side SM: 8.4 m2 each σx  1 cm; σψ  1°

A typical muon bundle event in Side DECOR ( 9 muons, 78 degrees) Y-projection X-projection

Muon bundle event (geometry reconstruction)

A “record” muon bundle event Y-projection X-projection

Muon bundle event (geometry reconstruction)

Results of muon bundle investigations

DECOR data. Muon bundle statistics Muon multiplicity Zenith angle range (*) Live time, (hour) Number of events  3 30 – 60 758 18137  5 1296 8864  10 2680 3272  60 1552 4109 10102 6786 10 19922 2013  75 395 (*) For zenith angles < 60°, only events in two sectors of azimuth angle (with DECOR shielded by the water tank) are selected.

Effective primary energy range Lower limit ~ 1015 eV (limited by DECOR area). Upper limit ~ 1019 eV (limited by statistics).

Local muon density spectra Low angles: around the “knee” θ = 50º : 1015 – 1017 eV θ = 65º : 1016 – 1018 eV Large angles: around 1018 eV

Basic results The following results based on local muon density spectrum measurements in the energy region 1015 - 1018 eV were obtained: - detection of the knee (this can be considered as energy scale calibration); - observation of the second knee; - some excess of muon bundles in comparison with predictions, which increases with energy. Important: Evidences for a similar excess of muons were found in some other EAS experiments.

Possible explanations The excess of muon density with the increase of energy in the interval 1015 – 1018 eV can be explained by three reasons: progressively heavier CR mass composition; progressive deficit of muons in EAS simulated with commonly used interaction models; inclusion of new processes of muon generation. In the favour of the last approach evident many unusual events detected in CR experiments.

List of unusual events In hadron experiments:  halos, alignment, penetrating cascades, long-flying component, large transverse momenta, Centauros, Anti-Centauros. In muon experiments:  excess of VHE (~ 100 TeV) single and multiple muons, observation of VHE muons, the probability to detect which is very small. Important: Unusual events appear at PeV energies of primary particles. From this point of view, results obtained in EAS investigations around the knee including uncertainties with mass composition can be considered as unusual, too:  change of EAS energy spectrum in the atmosphere, which is now interpreted as a change of primary energy spectrum.  changes of behavior of N(Ne) and Xmax(Ne) dependences, which are now explained as indication of heavier composition.

New physics in CR

What do we need to explain all unusual data? Model of hadron interactions which gives: Threshold behaviour (unusual events appear at several PeV only). 2. Large cross section (to change EAS spectrum slope). 3. Large yield of leptons (excess of VHE muons, missing energy and penetrating cascades). 4. Large orbital (or rotational) momentum (alignment). 5. More quick development of EAS (for increasing Nm / Ne ratio and decreasing Xmax elongation rate).

Possible variants Inclusion of new (f.e., super-strong) interaction. Appearance of new massive particles (supersymmetric, Higgs bosons, relatively long-lived resonances, etc.) Production of blobs of quark-gluon plasma (QGP) We considered the last model since it allows demonstrably explain the inclusion of new interaction.

Model of QGP production

Quark-gluon plasma Production of QGP provides two main conditions: - threshold behavior, since for that high temperature (energy) is required; - large cross section, since the transition from quark-quark interaction to some collective interaction of many quarks occurs: where R, R1 and R2 are sizes of quark-gluon blobs. 2. But for explanation of other observed phenomena a large value of orbital angular momentum is required.

Orbital angular momentum in non-central ion-ion collisions Zuo-Tang Liang and Xin-Nian Wang, PRL 94, 102301 (2005); 96, 039901 (2006)

Centrifugal barrier As was shown by Zuo-Tang Liang and Xin-Nian Wang, in non-central collisions a globally polarized QGP with large orbital angular momentum which increases with energy appears. In this case, such state of quark-gluon plasma can be considered as a usual resonance with a large centrifugal barrier. Centrifugal barrier will be large for light quarks but less for top-quarks.

Centrifugal barrier for different masses

How interaction is changed in frame of a new model? Simultaneous interactions of many quarks change the energy in the center of mass system drastically: where mc  nmN. At threshold energy, n ~ 4 ( - particle). Produced -quarks take away energy GeV, and taking into account fly-out energy t > 4mt  700 GeV in the center of mass system. Decays of top-quarks: ; W –bosons decay into leptons (~30%) and hadrons (~70%); b  c  s  u with production of muons and neutrinos.

Muon energy spectrum from top-quarks

How CR energy spectrum is changed? One part of t-quark energy gives the missing energy (e, , , ), and another part changes EAS development, especially its beginning, parameters of which are not measured. As a result, the measured EAS energy E2 will not be equal to primary particle energy E1 and the measured spectrum will be different from the primary spectrum. 3. Transition of particles from energy E1 to energy E2 gives a bump in the energy spectrum near the threshold.

Change of primary energy spectrum

How measured composition is changed in frame of the new approach Since for QGP production not only high temperature (energy) but also high density is required, threshold energy for production of new state of matter for heavy nuclei will be less than for light nuclei and protons. Therefore heavy nuclei (f.e., iron) spectrum is changed earlier than light nuclei and proton spectra!!!

Primary spectra of various nuclei

Measured spectra for some nuclei and spectrum of all particles

Influence of energy straggling

Comparison with experimental data (with 10% straggling)

Discussion of results Considered approach allows explain all unusual results obtained in cosmic rays including their energy spectrum and mass composition behavior. 2. Simplest model of energy spectrum surprisingly well describes experimental data. 3. Observed changes of composition are explained: a sharp increase of average mass at the expense of detection of EAS from heavy nuclei, after that, slow transition to proton composition.

Possibilities of new model check

How to check the new approach? There are several possibilities to check the new approach as in LHC experiments so in cosmic ray investigations. Of course, corresponding results can be obtained in LHC experiments, since QGP with described characteristics (excess of t-quarks, sharp increasing of missing energy, etc.), doubtless, will be observed. It is possible that some proof of this approach has been already obtained in lead-lead interactions at LHC (imbalance of jet energies in heavy ion collisions).

ATLAS observes striking imbalance of jet energies in heavy ion collisions (CERN Courier, January/February 2011) Highly asymmetric dijet event Dijet asymmetry distributions

How to explain the ATLAS results in frame of considered approach? t  W + + b In the top-quark center-of-mass system: Tb ~ 65 GeV, TW ~ 25 GeV. If to take into account fly-out energy, Tb can be more than 100 GeV. In the case if b gives a jet and W  ~ 20 , the ATLAS experiment’s picture will be obtained. But it is necessary to remark that to give exhaustive explanation of events observed in LHC experiments is very difficult.

How to check the new approach in cosmic ray experiments? One possibility is direct measurements of various nuclei spectra in space. Changes in spectra must begin from heavy nuclei. Two other possibilities are connected with VHE muon detection: - measurements of muon energy spectrum above 100 TeV; - measurements of energy deposit of EAS muon component below and above the knee. For that, existing muon and neutrino detectors can be used: BUST, IceCube, NEVOD-DECOR, Baikal, ANTARES, etc.

Prediction for CR nuclei spectra measurements

Preliminary results of muon energy spectrum investigations in Baksan Underground Scintillation Telescope (BUST) http://arxiv.org/pdf/0911.1692

IceCube results Double Coincident CRs High pT Muons Single Showers Bundle Data High pT Muon Double Coincident CRs High pT Muons Single Showers

Response of NEVOD for muon bundles

Energy deposit of muon bundles

Average energy of EAS muons in dependence on zenith angle and local muon density

Conclusion Results of NEVOD-DECOR and some other experiments in CR can be considered as an evidence in favour of new physics existence above the knee. The main feature of this new physics is appearance of an excess of very high energy muons (>100 TeV) in CR and their absence in collider experiments. Therefore today we have a unique possibility to prove the existence of new physics in cosmic rays by using existing muon and neutrino detectors: BUST, NEVOD-DECOR, IceCube, Baikal, ANTARES, etc. before it will be done in accelerator experiments.

Thank you for attention!

Proposal of NEVOD-DECOR-EAS experiment

Calibration Telescope System (CTS)

CTS response for EAS with energy 1016 eV

Proposal of EAS array around NEVOD-DECOR

Cluster on the roof of one building

Results of EAS simulation (1016 eV) NEVOD EAS

Cosmophysical approach to results of EAS investigations EAS energy is equal to the energy of primary particle. All changes of EAS characteristics are results of energy spectrum or/and composition changes only. Primary cosmic rays have galactic origin and their acceleration and keeping in Galaxy are determined by their charge Z or/and mass A. But experimental results of N/Ne and Xmax measurements contradict this approach. The problem of UHE cosmic ray origin is not clear.

Results of energy spectrum interpretation

Results of composition “investigations” Really, N / Ne – ratio is measured.

Results of Xmax measurements

Relation between primary energy E1 and measured energy E2 where t is total energy of top-quarks in the center-of-mass system. Threshold energy Eth, above which QGM blobs are produced, is determined by nucleus mass number Ai. In principle, compound mass mc may depend on Ai and E1 > Eth , too.

Simplest model mc = constant = nmN. where ln takes into account the increasing top-quark multiplicity and square root provides transition into the center-of-mass system. n = 4 n = 4

Existing approach to EAS analysis

New approach to EAS analysis

The ankle problem

Explanation of the ankle appearance On the face of it, the considered approach does not explain the behavior of the energy spectrum above the ankle, but this is not so. With the increase of primary particle energy, the excitation level in blob of QGM can exceed the centrifugal barrier, and it will decay into light quarks.

Illustration of the ankle appearance The knee 1017 eV 1018 eV The ankle In this case, there will be no missing energy and the measured spectrum begins to return to the initial form (g = 2.7) and to normal composition.

Solution of the ankle problem

The model of cosmic ray generation in plasma pinches B.A.Trubnikov, V.P.Vlasov, S.K.Zhdanov Kurchatov Institute, Moscow (Preprint № 4828/6 IAE, M., 1989; JETP Lett., 1989, v.49, p.581.) In cosmic plasma (of any origin) electrical discharges – "cosmic lightnings" can occur, at which cylindrical pinches are formed. Two basic instabilities of plasma pinches are known: snaky and neck. In the last case plasma jets are squeezed out of pinch neck. These jets are the accelerated particle beams. Snaky Neck

Energy spectrum of accelerated particles It is shown that energy distribution of particles in jets has the following form: which does not depend on pinch sizes, currents in pinches and other parameters. These parameters determine a proportionality coefficient only. Accelerated particle energy has no limitation since density in plasma pinch   when its radius  0. Therefore the contribution of various sources of cosmic plasma (stars, Supernovae, AGN, Galaxies, etc.) can be summed and a general spectrum in the whole Universe is formed.