Department of physics

Gaseous Based Detectors:

Under these category of detectors, the group took the responsibility along with BARC, Mumbai to set-up the lab for assembly and testing of Resistive Plate Chambers(RPC) for Muon Detector upgrade. The overall work included: Fabrication and testing in India and then testing, Installation and Commissioning of Indian RPC at CERN with CMS Detector. For this work a new gaseous detector development lab was setup in the department with 4 channel automatic gas mixing and distribution system. The CAMAC based DAQ is being upgraded with the VME based system.

Since the group is involved in the INO-ICAL (India based Neutrino Observatory-Iron Calorimeter) experiment which also uses RPCs as the active medium, it was obvious to use the existing facilities for the detector development work for the INO-ICAL. The RPCs used in INO are glass based where as the ones used in CMS are Bakelite based. The group has gained expertise in all the aspects of RPC fabrication, testing (using the cosmic test stand), scintillator paddles/telescope assembly and testing of its response, for both the glass as well as Bakelite.
Projects handled by the HEP Group

(Since 1999 till date)

Number of Projects: 8 (funded by DST, DAE-BRNS)

Total Amount of Projects: ~ Rs. 12.5 Crores

Project Proposals Approved (on-going/future collaboration)

The group has joined the Fermilab based neutrino program and has put forward a proposal to participate in the detector building for the Near detector as part of the Long-baseline neutrino experiment proposed by Fermilab.

Other than National Research Institutes, Panjab University has been a major centre being heavily supported by DST and DAE to have active participation in prestigious LHC(CERN) program. Govt. of India has placed the LHC program under Mega Project programe as India has Been recognized as Assosiate Member state of CERN and being considered as member state. The very active participation of this University in this Mega Project program has National interest.

A2. Theoretical High Energy Particle Group

Over the last 15 years both in collaboration with an International group based at the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy and independently Prof. C.S. Aulakh and his students have developed Left Right Supersymmetric models and the the Minimal Supersymmetric SO(10) Grand Unified Theory in a sustained way that has brought these theories to the point where these theories are now in active confrontation with the lates data from the LHC, Dark Matter experiments as well as contributing a testable locus for Lepto-Baryogenesis and Inflationary Cosmology. His work is well recognized by over 1800 citations in the International literature and has resulted in a number of invitations to speak at International Conferences, and direct national (SERC-THEP) and international (ICTP-Summer School in Particle Physics). The theory group has also established a High Performance Computation Centre with Tera-flop supercomputation facilities on a 80 node cluster. These facilities are expressly set up to be of use in the research program of the Theoretical High Energy Physics, Nuclear Physics and Condensed Matter Physics Groups which are already using them intensively.

The HEP theory group has made important contributions which are well recognized at the national and international level. Some of the well recognized contributions of the group concerns: (i) Formulation & analysis of consistent Minimal Super-symmetric models of the corresponding Grand Unified Theories, (ii) Texture specific mass matrices and CP violation, (iii) Proton Spin Crisis(iv) Study of existence and the stability of solitonic solutions of non-linear evolution equations. The group proposes to carry out the following activities in the coming year/s.

1. 
   Minimal Supersymmetric Grand Unified Theory:
   

In the last 7 years the generic class of left-right Supersymmetric Unified models was studied. This study together with Neutrino mass data led us to revive an SO (10) GUT model proposed by us in 1982 as the Minimal Supersymmetric GUT (MSGUT). This GUT is now known to be the minimal GUT compatible with all experimental data and is a focus of intense investigation by at least 5 groups worldwide. We developed a new method for analysing the group theory of SO(10) which enables us to calculate all group theoretic coefficients required. We have already calculated the complete spectrum and couplings at the GUT scale and used them to calculate the threshold corrections to the gauge couplings ab initio (for the first time in any GUT). We have also proposed a new scenario of Asymptotically strong unification based on this type of GUT.

In the coming year/s, we will further deepen our studies of the MSGUT and investigate the fermion spectra, GUT scale dynamical symmetry breaking, renormalization group fixed points and corrections, baryon decay and a host of other phenomenological issues that come into sharp focus once one has available the complete spectra and couplings of this MSGUT.

(b) Phenomenological Fermion Mass Matrices & CP Violation:

We have been carrying out intensive studies in the field of fermion mixings, CP violation and fermion mass matrices. In order to understand the quark mixing phenomenon at more fundamental level, texture specific mass matrices have been formulated at phenomenological level. Mass matrices based on discrete symmetry have also been studied with good results for the rare decays. Fermion flavour mixings, neutrino oscillations, neutrino mass matrices and CP violation in the leptonic sector continues to be the thrust areas at present. In the coming years, we plan to investigate intensively the possibility to find CP violation in the electronic sector and viable set of Fermion Mass matrices which are in agreement with the quark mixing and neutrino oscillation phenomena.

(c) Proton Spin Crisis:

We are also investigating the ‘proton spin crisis’ within chiral quark model with configuration mixings generated by gluon exchange. In the next two three years, we plan to investigate the gluon contribution to the spin angular momentum of the nucleon in the context of Chiral Constituent Quark Model.

(d) Nonlinear Evolution Equations of Physics

During the last few years, we studied the existence and the stability of Solitary Wave like solutions for various Nonlinear Evolution Equations of Physics interest. We find exact solutions to the nonlinear Schrödinger equation NLSE in the presence of self-steepening and a self-frequency shift. These include periodic solutions and localized solutions of dark-bright type which can be chiral, the chirality being controlled by the sign of the self-steepening term. A form of self-phase modulation that can be tuned by higher-order nonlinearities as well as by the initial conditions, distinct from the nonlinear Schrödinger equation, characterizes these solutions. In certain nontrivial parameter domains, solutions are found to satisfy the linear Schrödinger equation, indicating the possibility of linear superposition in this nonlinear system. Dark and bright solitons exist in both the anomalous and normal dispersion regimes, and a duality between the dark-bright type of solution and kinematics higher-order chirping is also seen. Localized kink solutions similar to NLSE solitons, but with very different self-phase-modulation, are identified.

The sol–gel system which is known, experimentally, to exhibit a power law decay of stress autocorrelation function has been studied theoretically. A second-order nonlinear differential equation obtained from Mori's integro-differential equation is derived which provides the algebraic decay of a time correlation function. Involved parameters in the expression obtained are related to exact properties of the corresponding correlation function. The algebraic model has been applied to Lennard-Jones and sol–gel systems. The model shows the behavior of viscosity as has been observed in computer simulation and theoretical studies. The expression obtained for the viscosity predicts a logarithmic divergence at a critical value of the parameter in agreement with the prediction of other theories.

For the first time, we find the complex solitons for a quasi-one-dimensional Bose–Einstein condensate with two- and three-body interactions. These localized solutions are characterized by a power law behavior.

The dynamic structure factor S(q, ω) of a harmonically trapped Bose gas has been calculated well above the Bose-Einstein condensation temperature by treating the gas cloud as a canonical ensemble of non-interacting classical particles. The static structure factor is found to vanish s8 q 2 in the long-wavelength limit. We also incorporate a relaxation mechanism phenomenological by including a stochastic friction force to study S(q, ω). A significant temperature dependence of the density fluctuation spectra is found. The Debye-Waller factor has been calculated for the trapped thermal cloud as a function of q and the number N of atoms. A substantial difference is found for small- and large-N clouds.

We studied the nonlinear dynamics of DNA, for longitudinal and transverse motions, in the framework of the microscopic model of Peyrard and Bishop. The coupled nonlinear partial differential equations for dynamics of DNA model, which consists of two long elastic homogeneous strands connected with each other by an elastic membrane, have been solved for solitary wave solution which is further generalized using Riccati parameterized factorization method.

We demonstrated that the competing cubic-quintic nonlinearity induces propagating soliton like dark (bright) solitons and double-kink solitons in the nonlinear Schrödinger equation with self-steepening and self-frequency shift. Parameter domains are delineated in which these optical solitons exist. Also, fractional-transform solitons are explored for this model. It is shown that the nonlinear chirp associated with each of these optical pulses is directly proportional to the intensity of the wave and saturates at some finite value as the retarded time approaches its asymptotic value. We further show that the amplitude of the chirping can be controlled by varying the self-steepening term and self-frequency shift.

Keeping in view the importance of dynamical invariants, attempts have been made to investigate complex invariants for two-dimensional Hamiltonian systems within the framework of the extended complex phase space approach. The rationalization method has been used to derive an invariant of a general non Hermitian quartic potential. Invariants for three specific potentials are also obtained from the general result.

During the last few years, various aspects of supersymmetric quantum mechanics and the application of this formalism to various physical situations have been studied. Some of the applications are in the area of information theory, in rearranging the information entropy in a given system, Nonlinear Physics, Atomic Physics and Particle Physics. We use a fractional transformation to connect traveling wave solutions of the nonlinear Schrödinger equation, phase-locked with a source, to the elliptic equations. Bright and dark solitons are obtained in the suitable range of parameter values.

(e) Noncommutative spaces and deformed symmetries

Although it has a longer history, the idea that configuration-space coordinates may not commute has arisen recently from string theory. Noncommuting spatial coordinates and fields can be realised in actual physical situations. Therefore, many physicists have investigated what follows just from the idea that coordinates are operators that do not commute. Noncommutative field theories have many novel features. We studied the general deformed conformal-Poincare (Galilean) symmetries consistent with relativistic (nonrelativistic) canonical noncommutative spaces. In either case, we obtained deformed generators, containing arbitrary free parameters, which close to yield new algebraic structures. We showed that a particular choice of these parameters reproduces the undeformed algebra. We also studied the deformed conformal-Poincare symmetries consistent with the Snyder-de Sitter space. A relativistic particle model invariant under these deformed symmetries was given. This model was used to provide a gauge independent derivation of the Snyder-de Sitter algebra. Our results were valid in the leading order in the parameters appearing in the model.

A3. Theoretical Astrophysics

We have recently started working on the galactic chemical abundance evolution (GCE). The idea is to understand the complete galactic elemental (isotopic) evolution of our galaxy and probably other galaxies. There has been revolutionary development in the stellar nucleosynthesic theories in almost all the stellar evolutionary models. As a result the GCE models could be made much more efficient now. We have been recently working on some of the aspects of GCE models and hopefully will be able to develop my own model. We will continue to work in GCE models for our galaxy and probably other galaxies. In addition, we would like to initiate some work in the laboratory simulation of irradiation of grains by energetic particles to study the production of short-lived nuclides that are found to be present in the early solar system.

The group has been working on the theoretical studies related with the origin and the early evolution of the solar system. In this regard, the thermal models related with the early evolution of planetesimals in the early solar system have been developed. This includes the planetary bodies that underwent large scale planetary scale melting and differentiation. The studies include the thermal evolution of icy planetesimals and trans-Neptunian objects. Further, the work is going on for the processes that triggered the formation of the solar system and planetary bodies.

The group has extensive cordial, professional relationship with other Institutions through collaborations and visits. The faculty participates in International / national workshops, seminars and conferences and invites visitors under TPSC programme. Participation in Indian Neutrino Initiative (INO), Associateship at ICTP, Visiting Scientist position at IUCAA, DAAD fellowship are some of the honors the group received recently. With this expertise, the group is confident in holding Winter /Summer schools and take up long term collaborative research projects.

(B). Nuclear Physics

Experimental Activities

In House Facilities:

B1. Chandigarh Variable Energy Cyclotron:

Current activities:

Chandigarh Variable Energy Cyclotron is an unique facility amongst the Universities in India. It has been functioning satisfactorily since last many years. This machine has been mainly used to produce 3.0 MeV protons in the last few years and is being used as a regional facility for PIXE, PIGE and polymer irradiation experiments. A new beam line (zero degree) for general purpose experiments is under progress.

(a) PIXE and PIGE Programme:

The low-energy proton beam (~ 3 MeV) is very much suitable for elemental analysis using PIXE and PIGE techniques. At present, Cyclotron is being used effectively for determination of trace elements in Archaeological, bio-medical sciences, Forensic science, aerosol samples etc. Our next aim is to make use of PIGE and RBS facilities along with PIXE for elemental analysis for a variety of samples from various fields. PIGE facility will be used for the detection of light elements such as Li, B, F, Na. Mg, Al, Si and P for which PIXE technique is not suitable. The main thrust of PIGE program will be the elemental analysis of Boron in biological samples, Fluoride in water samples, detection of Al and Si in aerosol samples. PIXE and PIGE techniques will also be employed to the study of elemental constituents of some traditional medicinal plants generally used in curing many diseases and in commonly edible vegetables of medicinal and pharmacological importance. RBS facilities will be used for elemental analysis and depth profiling of the thin films. This programme will be continued for next five years.

(b) Irradiation Work:

The Studies on the effect of low energy (2 to 3) MeV proton beam irradiation on polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), ethyle vinyl acetate (EVA), polycarbonate (PC) and blended PVC/PET have been investigated at different fluences. Now the focus on polymer nano composites films have been planned for future work. Polymeric films will be synthesized by the dispersion of different concentration of nanoparticles in the polymer matrix using sol gel technique.  This work is being done in collaboration with M S University of Baroda, Vadodara. It is planned to strengthen collaboration with other Indian universities for PIXE/PIGE and irradiation experiments in the cyclotron lab.

It is planned to Establish an experimental set up for the (p,γ) and (α,γ) reactions at the Cyclotron of the Department. It is planned to set up neutron activation using proton beam from the cyclotron. Recently, old power supplies of the cyclotron magnet systems were replaced by solid state power supply, by the funding from the departmental CAS programme and a DST project for the regional PIXE programme. At present this is the only accelerator in the country available for low energy proton and alpha beam in the above energy range. We propose to upgrade the existing experimental set up and start a programme for measuring (p,γ) and (α,γ) reaction cross sections which has a direct relevance for nuclear astrophysics and nuclear data. This programme will be use full as a training ground for students of M.Sc., Ph.D. and post-M.Sc. course in accelerator physics of the department, besides its nuclear physics importance. The group efforts for next five years will also be useful for the proposed 5 MV accelerator of the Panjab University. We will need a new HPGe detector and we will also explore to repair the old HPGe detector for measuring life time of the astrophysically important nuclei using DSAM technique.

B2. Establishment of a New 5 MV Electrostatic Accelerator:

In the next five years it is planned to concentrate on a major proposal for 5 MV Tandetron accelerator. The proposal is already defended before the Expert Committee of the DST, Govt. of India. In the next new few months we are expecting final decision from DST. The cost estimate has been projected to be Rs.60 Crores for the main machine, beam lines and some major experimental apparatus. The recurring expenditure will be about 2 Crores which include the salary of the staff, running cost of the machine and arrangement for carrying out the research programme. The facilities will also be extended to other universities and institutes in the country. Planned research programs using 5 MV Tandetron facility are (i) Cluster Physics, (ii)Neutron generation, (iii)Accelerator Mass Spectrometry, (iv) Material modification, and (v) Characterization using Analytical techniques : RBS, PIXE, PIGE, ERDA, NRA, Micro-beam facility and a time-of-flight set-up for heavy ion RBS, Masked ion beam lithography (vi) Nuclear Astrophysics (vii) PAC Experiments. It will also be used for production of radioisotopes for medical/industrial uses – New radioactive probes for PAC studies, PET sources, Positron sources for positron annihilation investigations and radio-active sources for commercial values. In addition, beam will also be given for detector testing facility – for International collaborations and Radiation damage testing of silicon detectors.

B3. Activities at National/ International Level:

Nuclear Structure at High Spins:

The group has been investigating the high spin states in the nuclei populated through fusion-evaporation reactions using heavy-ion beams from pelletron accelerators at the IUAC and TIFR accelerator facilities. Reactions have been investigated through in-beam -ray spectroscopic techniques using the Clover detector spectrometers INGA for gamma-spectroscopy studies. The following investigations have been carried out during the recent past:

(a) Excited states in the ⁹⁹Pd nucleus populated in the ⁷⁵As (²⁸Si, p3n) fusion-evaporation reaction at E_lab = 120 MeV have been investigated through in-beam g -ray spectroscopic techniques using an array of Compton suppressed clover detectors. The level scheme is established up to excitation energy ~11.5 MeV and spin ~ 25ħ with the addition of about 60 new transitions. The level structures observed in 99Pd have been interpreted in the framework of a microscopic theory based on the deformed Hartree-Fock and angular momentum projection techniques. Band structures at lower spins are based on the low -Ω νg_7/2 and vd_5/2 orbitals, and those at higher spins are reproduced for the π(g_9/2)⁵ Ä π(g_7/2) Ä ν(g_7/2)²Ä ν(h_11/2)² Ä ν(g_9/2)⁻¹ and π(g_9/2)⁶ Ä ν(g_9/2)¹⁰ Ä ν(g_7/2)² Ä ν(h_11/2) configurations. The octupole correlations in ⁹⁹Pd have been inferred from new interband E1 transitions linking the D I = 1 states of the bands based on the νh11/2 and νd5/2 orbitals (l = 3, j = 3, and D π = −1) with the deduced B(E1) values ~ 10⁻⁶ W.u.

(b) High spin states in neutron-deficient ^106,107In were investigated using ⁷⁸Se (₃₂S, pxn) reaction at 125 MeV. The de-excitations were studied using in-beam g -ray spectroscopic techniques involving the Compton-suppressed clover detector array. The level schemes are extended up to 7 MeV of excitation energy and spin ~ 22 ħ. In ¹⁰⁶In, the negative parity states constituting four dipole bands have been observed. The positive parity states mainly exhibit single-particle excitations. Projected deformed Hartree-Fock calculations were carried out in ^106,107In to understand the configurations of different bands in this nucleus. Various bands are reproduced in band mixing calculations with the configurations involving high-Ω πg_9/2 and νd_5/2 orbits, and low-Ω πg_7/2, νg_7/2 and νh_11/2 orbits.

(c) High spin states in 112In were investigated using the ¹⁰⁰Mo(¹⁶O, p3n) reaction at 80 MeV. The excited level has been observed up to ~ 6 MeV excitation energy and spin ~20ħ with the level scheme showing three dipole bands. Polarization and lifetime measurements were carried out for the dipole bands. Tilted axis cranking model calculations were performed for different quasiparticle configurations of this doubly odd nucleus. Comparison of the calculations of the model with the B(M1) transition strengths of the positive- and negative-parity bands firmly established their configurations.

(d) Excited states in ¹³¹Cs were investigated through in-beam g -ray spectroscopic techniques following its population in the ¹²⁴Sn(¹¹B, 4n) fusion-evaporation reaction at a beam energy of 46 MeV. The previously known level scheme has been substantially extended up to ~9 MeV excitation energy and 49/2ħ spin with the addition of seven new band structures. The present level scheme consisting of 15 bands exhibits a variety of collective features in this nucleus at intermediate spin. The excitation energies of the observed levels in different bands and the corresponding ratios of transition strengths, i.e., B(M1)/B(E2), have been compared with the results of projected deformed Hartree-Fock calculations based on various quasiparticle configurations. A strongly coupled band has been reassigned a high-K three-quasiparticle πh_11/2 Ä νh_11/2 Ä νd_3/2 configuration based on the properties of this band and that of its new coupled side band. The configurations of these bands are also discussed in the framework of tilted-axis cranking model calculations and the systematics of the odd-A Cs isotopes. Additional three energetically closely placed coupled bands have been assigned different unpaired three-quasiparticle configurations. g -vibrational bands coupled to the πh_11/2 and πg_7/2 single-particle configurations have been reported in this nucleus. Observation of new E1 transitions linking the opposite-parity πh_11/2 and πd_5/2 bands provides fingerprints of possible octupole correlations.

(e) A bandlike structure, based on the πh_11/2Äνh_11/2 configuration, has been identified for the first time in ¹³⁴Cs in a gamma-ray spectroscopic study using fusion evaporation reactions. The nature of this band in ¹³⁴Cs has been found to be distinctly different than the nearly degenerate doublet rotational band structures, observed in the lighter Cs isotopes for the same configuration. Both the total Routhian surface and the tilted axis cranking calculations were performed to understand the experimental observations. The present results suggest that the N = 77 defines the border of the deformed structure in the A ~130 region while approaching N = 82.

(f) The ¹²²Sn(¹¹B,4n) fusion-evaporation reaction at E_lab=60 MeV was used to populate excited states in ¹²⁹Cs, and the deexcitations were investigated using in-beam γ-ray spectroscopic techniques. The level scheme of ¹²⁹Cs is established up to ~8MeV excitation energy and 47/2ħ spin. The observed band structures are interpreted for their configurations in the framework of cranking model calculations and systematic of the neighboring ₅₅Cs isotopes. A negative-parity I=1 coupled band has been assigned the h_11/2(νh_11/2)2 configuration as solution of the tilted-axis cranking, which coexists with the πh_11/2 yrast band resulting from the principal-axis cranking. A new band has been identified as a γ-vibrational band built on the πh_11/2 orbital. A pair of strongly coupled positive-parity bands exhibiting similar features have been assigned different unpaired three-quasi-particle configurations involving the h_11/2νh_11/2 component. The previously identified unfavored signature partners of the πd_5/2 and πg_7/2 bands are reassigned as γ vibrations of the core coupled to the πg_7/2 single-particle configuration, and the favored signature of the πd_5/2 band, respectively.

(g) We carried out the experiment using INGA to study the high spin structure in ^130,131Ba using ¹³C + ¹²²Sn at 65 MeV. Preliminary results have been presented in DAE symposium and final results are being prepared to send for publication in some referred journal.

(h) We have proposed the ²⁸Si + ¹¹⁶Cd reaction at 115 MeV to study the high spin structure in ¹⁴⁰Pm and ¹⁴⁰Sm. This experiment will be carried out at TIFR, Mumbai using INGA in phase –II run.

In the future experiments, it is planned to use HYRA for recoil tagging of heavy nuclei, and the ancillary equipments - charged particle ball. Active participation of the group will be there in setting up of the world class facility along with the other ancillary equipments at IUAC. Life time measurements of excited nuclei will be continued through DSAM and RDM techniques.