International Workshop on Grand Unified Theories: Current Status and Future Prospects

17 Dec 2007, 08:00 → 19 Dec 2007, 19:00 Europe/Zurich

Epoch Ritsumei 21 (Ritsumeikan University)

Nobuchika Okada (KEK), Nobuhiro Maekawa (Nagoya University), Taichi Kugo (Yukawa Institute for Theoretical Physics), Takeshi Fukuyama (Ritsumeikan University; Chair), Yoshiharu Kawamura (Shinsyu University), Yoshio Koide (Osaka University), Yutaka Hosotani (Osaka University)

Scope of the Workshop: There are many reasons that need the theory beyond the Standard Model. From the observational side, neutrino mass, the existence of Dark Matter, etc. indicate it. From the theoretical side, there are more reasons: the gauge coupling unification, Higgs mass hierarchy, Dark Matters, Baryon number asymmetry etc. Supersymmetric (SUSY) Grand Unified Theories (GUT) are the most promising candidate to satisfy the above mentioned requirements. There are accumulated so far many information from Neutrino Oscillation, Accelerator experiments, and Cosmological Observations. Also Large Hadron Collider (LHC) begin to work this year. So it is very timely to hold the Workshop on GUT in this year. In the usual conferences, GUT is one of the themes and the concentrated discussions were not sufficient. In this Workshop we restrict on GUT in relatively small conference scale , and the concentrated and long-time discussions become possible. In order to realize such atmosphere, we had the program that includes a few but long talks by the leading scientists on this region. They stand either on common ground or on the different stand points. We can enjoy comprehensive and diverse view points.

Monday 17 December

registration

Plenary Talks

1 Welcome to Ritsumeikan University

2 Scope of Workshop and Organization questions

Speaker: Prof. Takeshi Fukuyama (Ritsumeikan University)

09:15 break

3 Does the extra dimension rescue the SO(10) GUT?

Speaker: Prof. Takeshi Fukuyama (Ritsumeikan University)

Slides Private_view.pdf Private_view.ppt

4 Review of phenomenological models

Speaker: Dr Koichi Matsuda (Tsinghua University)

Slides matsuda.pdf matsuda.ppt

10:30 break

5 Discrete Gauge Symmetries and Proton Stability in grand unified theories

We discuss the results of a search for anomaly free Abelian Z_N discrete symmetries that lead to automatic R-parity conservation and prevents dangerous higher-dimensional proton decay operators in simple extensions of the minimal supersymmetric extension of the standard model (MSSM) based on the left-right symmetric group, the Pati-Salam group and SO(10). We require that the superpotential for the models have enough structures to be able to give correct symmetry breaking to MSSM and potentially realistic fermion masses. We find viable models in each of the extensions and for all the cases, anomaly freedom of the discrete symmetry restricts the number of generations.

Speaker: Prof. Rabindra. N. Mohapatra (University of Maryland)

Slides Mohapatra_japan07.pdf Mohapatra_japan07.ppt

6 B-aniti-B mixing and lepton flavor violation in supersymmetric grand unified models

We study B-anti-B mixing in grand unified SO(10), SU(5) models where the mixings among the second and third generation squarks arise due to the existence of flavor violating sources in the Dirac and Majorana couplings which are responsible for neutrino mixings. We find that when the branching ratio of tau->mu gamma decay is enhanced to be around the current experimental bound, B_s-anti-B mixing may also contain large contribution from supersymmetry in the SO(10) boundary condition. We also study the constraint arising from the recently observed D-anti-D mixing. In the left-right symmetric unified models, the supersymmetric contributions in the mixing amplitudes of D-anti-D, K-anti-K and B-anti-B are all correlated. We compare the constraint from the D-D mixing with the K-anti-K mixing and find that the D-anti-D mixing constrains the maximal supersymmetric contribution to the B_s-anti-B_s mixing amplitude. The maximal supersymmetric contribution can allow a large CP phase of B_s-anti-B_s mixing which can be tested by the ongoing measurement of the phase of B_s -> J/psi phi decay.

Speaker: Dr Yukihiro Mimura (Texas A&M University)

Slides mimura-flavor.pdf mimura-flavor.ppt

7 Unparticle Dark Matter

Once a parity is introduced in unparticle physics, under which unparticle provided in a hidden conformal sector is odd while all Standard Model particles are even, unparticle can be a suitable candidate for the cold dark matter (CDM) in the present universe through its coupling to the Standard Model Higgs doublet. We find that for Higgs boson mass in the range, 114.4 GeV < m_h < 250 GeV, the relic abundance of unparticle with mass 50 GeV < m_U < 80 GeV can be consistent with the currently observed CDM density. In this scenario, Higgs boson with mass m_h < 160 GeV dominantly decays into a pair of unparticles and such an invisible Higgs boson may be discovered in future collider experiments. Ref.: e-Print: arXiv:0711.1506 [hep-ph]

Speaker: Dr Tatsuru Kikuchi (KEK)

Slides Unparticle_Dark_Matter_(GUT07).pdf Unparticle_Dark_Matter_(GUT07).ppt

Lunch time break

Plenary Talks

8 Differentiating Neutrino Models on the Basis of the Reactor Angle and Lepton Flavor Violation

An earlier survey of viable neutrino mass and mixng models revealed a broad spectrum of predicted valies for sin^2 (theta_13) ranging fom the present upper bound of 0.04 accessible to the next round of reactor neutrino experiments down to values less than 0.001 requiring a neutrino factory for observation. Here we single out models with similar theta _13 predictions ad show that the viability of each type can be further differentiated according to their predictions for the l_j to l_i lepton flavor-violating branching ratos for various of the CMSSM parameters. Thi study supplements previous results obtained on the theta_13 - lepon flavor violation connection which involked restrictions on the class of SUSY GUT seesaw models considered.

Speaker: Prof. Carl. H. Albright (Northern Illinois University and Fermilab)

Slides Albright_IWGUT07.pdf

9 Nucleon sigma term from lattice QCD

There has been renewed interest in the nucleon sigma term - the scalar form factor of the nucleon at zero recoil- since it determines the dark matter reaction rate with nucleon through the t-channel Higgs boson exchange. Despite its importance and its long history of theoretical studies, there are still substantial uncertanties. We present our recent studies of the nucleon sigma term based on the JLQCD project of Nf=2 unquenched lattice QCD simulation with dynamical overlap fermion.

Speaker: Prof. Tetsuya Onogi (YITP, Kyoto University)

Slides Onogi_GUT_ver5.pdf Onogi_GUT_ver5.ppt

15:40 break

10 Proton decay in SO(10) with stabilized doublet-triplet splitting

Speaker: Prof. Kaladi. S. Babu (Oklahoma State University)

Slides gut_babu.pdf gut_babu.ppt

11 New Physics in Colliders

Speaker: Dr Nobuchika Okada (KEK)

Slides GUT07-Okada.pdf GUT07-Okada.ppt

12 How to Evade a NO-GO Theorem in Flavor Symmetries

We may expect that an approach based on symmetries will be a powerfulinstrument for investigating the origin of the flavors. However, when we want to introduce a symmetry (discrete one, U(1), and any others) into our mass matrix model, we always encounter an obstacle, the so-called No-Go theorem in flavor symmetries (YK, Phys.Rev. D71 (2005) 016010). In the present talk, I would like to talk about how to evade this No-Go theorm in order to build a realistic mass matrix model. I will suggest three ways to evade the theorem.

Speaker: Prof. Yoshio Koide (Osaka University)

Slides koideGUT3.pdf koideGUT3.ppt

Welcome drink

Tuesday 18 December

Plenary Talks

13 Family Symmetry and GUTs

Speaker: Prof. Steve. F. King (University of Southampton)

Slides king.pdf

14 Proton Decay and Flavor Violating Thresholds in SO(10) Models

Discovery of neutrino mass has put the spotlight on supersymmetric SO(10) as a natural candidate for grand unification of forces and matter. However, the suppression of proton decay is a major problem in any supersymmetric grand unified models. In this paper we show how to alleviate this problem by simple threshold effect which raises the colored Higgsino masses and the grand unification scale to \gtrsim 10^{17} GeV. There exist only four types of fields arising from different SO(10) representations which can generate this kind of threshold effects. Some of these fields also generate a sizable flavor violation in the quark sector compared to the lepton sector. The b-\tau unification can work in these types of models even for intermediate values of tan\beta.

Speaker: Dr Yukihiro Mimura (Texas A&M University)

Slides mimura-GUT07-02.pdf mimura-GUT07-02.ppt

10:40 break

15 String compactification and unification of forces

Speaker: Prof. Jihn. E. Kim (Seoul National University)

Slides KimJE.pdf KimJE.ppt

16 Three family GUT-like models from heterotic string

We recently developed string compactification on non-factorizable orbifold. Especially in E8xE8 Heterotic string, we obtain SU(5) and SO(10) GUT-like models with simple assumptions. These models have simple spectra including three generations of matter and messenger-like sectors.

Speaker: Mr Kei-Jiro Takahash (Kyoto University)

Slides Takahashi_07-12-18_workshop-GUT.pdf Takahashi_07-12-18_workshop-GUT.ppt

Lunch time break

Plenary Talks

17 CP and SUSY breaking and E6 GUT

Speaker: Prof. Nobuhiro Maekawa (Nagoya University)

Slides Maekawa_E6RitsumeikanF.pdf Maekawa_E6RitsumeikanF.ppt

18 Scalar non-degeneracy and flavor unification

A general consequence of GUT is unification of flavor. It is shown that the non-degeneracy of scalar superparticles provides a direct imprint of flavor structure in high-energy fundamental theory.

Speaker: Mr Kentaro Kojima (Kyusyu University)

Slides KOJIMA_GUT07.pdf KOJIMA_GUT07.ppt

15:10 break

19 Gauge-Higgs Unification

Speaker: Prof. Yutaka Hosotani (Osaka University)

Slides Hosotani_ritsumei-Dec07-short.pdf

20 Towards a Realistic Grand Gauge-Higgs Unification

We investigate a 5D SU(6) grand gauge-Higgs unification model compactified on an orbifold S^1/Z_2. Ordinary quarks and leptons, together with right-handed neutrinos, are just accommodated into a minimal set of representations of the gauge group, without introducing any exotic states. The proton decay turns out to be forbidden at least at the tree level. We also find a correct electroweak symmetry breaking SU(2)_L \times U(1)_Y \to U(1)_{em} is easily realized by introducing suitable number of adjoint fermions.

Speaker: Dr Nobuhito Maru (Kobe University)

Slides Maru_GUT07.pdf

21 Search for a realistic orbifold grand unification

Speaker: Prof. Yoshiharu Kawamura (Shinshu University)

Slides KawamuraOGUT.pdf

22 Building a model by coset space dimensional reduction using 10 dimensional coset spaces

Most of the free parameters in the SM are contained in the Higgs potential terms and the Yukawa coupling terms, i.e the Higgs associated terms. This fact suggests that if the origin of the Higgs particle results in a more fundamental model, this model would be described by fewer free parameters. One of the candidates of the model that gives origin of the Higgs particles is a gauge-Higgs unification model. Among these ideas we are interested in gauge-Higgs unification models based on the coset space dimensional reduction(CSDR) scheme. In CSDR, we assume the fundamental model is gauge theory in higher dimensional space-time that has extra dimensions of coset space structure. we investigate models based on CSDR scheme using 10 dimensional coset spaces.

Speaker: Mr Takaaki Nomura (Saitama University)

Slides GUT07-Nomura.pdf GUT07-Nomura.ppt

23 Gauge unification in 5-D SU(5) model with orbifold breaking of GUT symmetry

We consider a 5-dimensional SU(5) model wherein the symmetry is broken to the 4-dimensional Standard Model by compactification of the 5th dimension on an S^1/(Z_2 imes Z^prime_2) orbifold. We identify the members of all SU(5) representations upto 75 which have zero modes. We examine how these light scalars affect gauge coupling unification assuming a single intermediate scale and present several acceptable solutions. The 5-D compactification scale coincides with the unification scale of gauge couplings and is determined via this renormalization group analysis. When SO(10) is considered as the GUT group there are only two solutions, so long as a few low dimensional scalar multiplets upto 126 are included.

Speaker: Prof. Biswajoy Brahmachari (Vidyasagae Evening College)

Slides brahmachari-gut2007.pdf

Welcome Banquet

Wednesday 19 December

Plenary Talks

24 Probing Unification Scale Physics at TeV-scale Collider Experiments

Grand Unification and seesaw mechanism of neutrino mass are physics at extremely high energies, which may not allow for direct experimental tests. Here I will discuss how we may obtain information about such extreme high energy physics based on TeV-scale collider data, such as LHC and ILC.

Speaker: Prof. Hitoshi Murayama (University of California, Berkeley and Institute for the Physics and Mathematics of the Universe, University of Tokyo)

Slides

• amplitude.avi
• inflaton.avi
• Ritsumeikan_2007.pdf
• Ritsumeikan_2007.ppt
• scalefactor.avi

25 Higgsless breaking of Grand Unification

We consider a possibility of higgsless breaking of the grand unified symmetry. In contrast with the orbifold breaking, the rank can be reduced in this breaking. We apply this breaking to a 5D SO(10) model.

Speaker: Dr Toshifumi Yamashita (Osaka University)

Slides GUT07-TYamashita-2.pdf GUT07-TYamashita-2.ppt

26 A three Site Higgsless Model

Speaker: Dr Masafumi Kurachi (YITP, Kyoto University)

Slides kurachi.pdf

10:30 break

27 SUSY and Cosmology -- inflation, gravitino, and axion

Speaker: Prof. Masahiro Kawasaki (ICRR, University of Tokyo)

Slides Kawasaki_susy_cosmology.pdf

28 Inflation and Unification

Speaker: Prof. Qaisar Shafi (Bartol Research Institute and Delaware University)

Slides Shafi_gut07_final.pdf

12:40 End of the workshop