Final Report Summary - FLUENT (Flavour, unifications and experimental tests)
The flavour structure of matter remains one of the deepest challenges to our current understanding of the elementary particles and their interactions. Indeed, even after more than half century of intense research the flavour patterns underlying most of the high-energy physics processes defies our comprehension. The Standard Model of particle physics, the best description of the sub-nuclear world ever conceived, does not provide any clues to why we observe just three families of quarks and leptons, what is the origin of their peculiar quantum-mechanical mixing or why their masses range over more than twelve orders of magnitude.
With the advent of the next generation of particle physics experiments, in particular the Large Hadron Collider, the high-precision neutrino facilities, large-volume rare decay detectors and other kinds of instruments and techniques focusing on uncovering the physics beyond the Standard Model, there is a growing and well-founded expectation that the next decade could witness the first glimpse on these mysteries.
The FLUENT project was focusing on these fundamental problems from the perspective of the grand unification, one of the best motivated hypotheses about the nature of the dynamics governing the very birth of the Universe. In a wider perspective, its main aim was to deepen the current understanding of the elusive low-energy imprints of physics at very high energies as a virtually unique strategy for testing the unification paradigm.
To this end, there were three basic directions addressed in most of the work done: firstly, there is the still-ongoing quest for the minimal potentially realistic grand-unified theory (GUT) as a maximally predictive instance of the grand-unified quantum field theory with the aim to support the experimental efforts at the next generation of the large-volume facilities with high quality theoretical inputs; these would not only serve as a clear motivation for further development of the experimental high-energy physics enterprise but also as a door to an ultimate testability of the simplest unified models of the three forces governing the physics at microscopic scales. In this respect, the most interesting result achieved throughout the project execution is certainly the full rehabilitation of the most minimal renormalisable non-supersymmetric SO(10) grand unification, a beautiful and a particularly simple GUT model that has been almost forgotten since mid-1980's when it was claimed unpromising due to peculiar tachyonic instabilities plaguing all of its potentially realistic classical vacua. Remarkably enough, as shown in a recent series of the fellow's works on this subject, such generic tachyonic instabilities are mere artifacts of the classical approach and there is a plenty of stable and potentially realistic vacuum configurations available at the quantum level. On top of that, an extended analysis of the quantum structure of the theory made it clear that also the second traditional argument against the minimal SO(10) GUT, i.e. a stringent upper bound on the scale of the B-L violation apparently incompatible with the popular seesaw justification of the smallness of the light neutrino masses is not entirely general and that this theory actually does possess extended regions in the parameter space where the standard seesaw mechanism can be perfectly supported. Moreover, in this regime, the same model predicts light coloured remnants that can be accessible at the LHC and which, in principle, can even account for the peculiar enhancement of the partial Higgs decay width into two photons reported recently by both ATLAS and CMS collaborations.
The second line of research followed throughout the project execution was a series of detailed studies of flavour aspects of simple supersymmetric SO(10) unified models motivated by the common belief that the LHC would soon provide the first data on the supersymmetric spectrum together with the expected arrival of the unprecedented-quality data from the new generation of neutrino experiments such as Daya Bay, RENO and Double Chooz focusing on the measurement of the last undetermined mixing angle in the lepton sector. To this end, the fellow has been studying namely the possible imprints of the intermediate-scale extended gauge symmetries in the low-energy superpartner spectrum measurable at the LHC, the impact of a potential mixing among the standard chiral matter and hypothetical extra vector-like multiplets in simple supersymmetric GUTs focusing on their implications for the lepton mixing pattern as well as effects of other non-standard interactions in the upcoming neutrino experiments that may obscure the determination of the quantities of main interest. Among the most interesting results of this part of the project one should mention namely the strong preference of relatively large values of the leptonic 1-3 mixing angle and small Dirac CP phases observed in the simplest supersymmetric SO(10) GUTs with vector-like extra matter (note that the former result is, indeed, perfectly compatible with the latest measurements) and a relatively high non-standard interactions discrimination potential predicted for the Daya Bay experiment.
In the third research line entertaining namely the virtues of the bottom-up approach to the extended gauge symmetries and grand unification, a special attention was paid namely to the fine correlations between the high-energy inputs governing the structure of the unified theories and the low-energy data and, in particular, the consistency and precision of the theoretical methods behind. Given the fellows expertise in renormalisation and symmetry aspects of gauge theories the main efforts here were spent on the fine effects of the so-called kinetic mixing inherent to theories with multiple abelian symmetry factors in their gauge group and their consistent implementation in the high precision calculations. The most important result attained in this direction was presumably the finalisation of the fundamental project launched by S. Martin and M. Vaughn in early 1990's focusing on the complete calculation of the structure of the two-loop renormalisation group in softly broken supersymmetric gauge theories. The relevant study was based on an original method developed by the fellow exploiting a simple residual reparametrisation invariance of a general gauge theory which provided a relatively straightforward recipe for generalising the existing results valid for utmost one U(1) gauge factor to the case of an arbitrary gauge group.
In conclusion, the project contributed significantly to the field of precision beyond Standard-Model physics by providing several highly interesting original result as well as new methods within its classical subjects such as grand unification and other extended gauge symmetries with a clear potential impact on developing a better understanding of the interplay among physics at vastly different energy scales. This, in turn, can shed more light on some of the fundamental questions about the origin and destiny of the Universe and the matter, radiation and other constituents within.
The results obtained so far are covered in the following peer-reviewed publications:
- Physical Review D83, 035002 (2011),
- Physical Review D83, 035018 (2011)
- Journal of High Energy Physics 12, 001 (2011),
- Physical Review D84, 053012 (2011),
- Nuclear Physics B854, 28 (2012),
- Journal of High Energy Physics 02, 084 (2012),
- Physical Review D85, 095014 (2012)
together with a couple of proceedings contributions:
- Journal of Physics: Conference Series 259 (2010) 012098,
- AIP Conference Proceedings 1467, 37 (2012).
Further information on the project execution is available at the dedicated website: http://www-ucjf.troja.mff.cuni.cz/~malinsky/fluent
The current fellow's affiliation is: Institute of Particle and Nuclear Physics
Faculty of Mathematics and Physics of the Charles University in Prague
V Holesovickach 2, 180 00 Praha 8, Czech Republic
Email: malinsky@ipnp.troja.mff.cuni.cz
Phone: +42-022-1912438
With the advent of the next generation of particle physics experiments, in particular the Large Hadron Collider, the high-precision neutrino facilities, large-volume rare decay detectors and other kinds of instruments and techniques focusing on uncovering the physics beyond the Standard Model, there is a growing and well-founded expectation that the next decade could witness the first glimpse on these mysteries.
The FLUENT project was focusing on these fundamental problems from the perspective of the grand unification, one of the best motivated hypotheses about the nature of the dynamics governing the very birth of the Universe. In a wider perspective, its main aim was to deepen the current understanding of the elusive low-energy imprints of physics at very high energies as a virtually unique strategy for testing the unification paradigm.
To this end, there were three basic directions addressed in most of the work done: firstly, there is the still-ongoing quest for the minimal potentially realistic grand-unified theory (GUT) as a maximally predictive instance of the grand-unified quantum field theory with the aim to support the experimental efforts at the next generation of the large-volume facilities with high quality theoretical inputs; these would not only serve as a clear motivation for further development of the experimental high-energy physics enterprise but also as a door to an ultimate testability of the simplest unified models of the three forces governing the physics at microscopic scales. In this respect, the most interesting result achieved throughout the project execution is certainly the full rehabilitation of the most minimal renormalisable non-supersymmetric SO(10) grand unification, a beautiful and a particularly simple GUT model that has been almost forgotten since mid-1980's when it was claimed unpromising due to peculiar tachyonic instabilities plaguing all of its potentially realistic classical vacua. Remarkably enough, as shown in a recent series of the fellow's works on this subject, such generic tachyonic instabilities are mere artifacts of the classical approach and there is a plenty of stable and potentially realistic vacuum configurations available at the quantum level. On top of that, an extended analysis of the quantum structure of the theory made it clear that also the second traditional argument against the minimal SO(10) GUT, i.e. a stringent upper bound on the scale of the B-L violation apparently incompatible with the popular seesaw justification of the smallness of the light neutrino masses is not entirely general and that this theory actually does possess extended regions in the parameter space where the standard seesaw mechanism can be perfectly supported. Moreover, in this regime, the same model predicts light coloured remnants that can be accessible at the LHC and which, in principle, can even account for the peculiar enhancement of the partial Higgs decay width into two photons reported recently by both ATLAS and CMS collaborations.
The second line of research followed throughout the project execution was a series of detailed studies of flavour aspects of simple supersymmetric SO(10) unified models motivated by the common belief that the LHC would soon provide the first data on the supersymmetric spectrum together with the expected arrival of the unprecedented-quality data from the new generation of neutrino experiments such as Daya Bay, RENO and Double Chooz focusing on the measurement of the last undetermined mixing angle in the lepton sector. To this end, the fellow has been studying namely the possible imprints of the intermediate-scale extended gauge symmetries in the low-energy superpartner spectrum measurable at the LHC, the impact of a potential mixing among the standard chiral matter and hypothetical extra vector-like multiplets in simple supersymmetric GUTs focusing on their implications for the lepton mixing pattern as well as effects of other non-standard interactions in the upcoming neutrino experiments that may obscure the determination of the quantities of main interest. Among the most interesting results of this part of the project one should mention namely the strong preference of relatively large values of the leptonic 1-3 mixing angle and small Dirac CP phases observed in the simplest supersymmetric SO(10) GUTs with vector-like extra matter (note that the former result is, indeed, perfectly compatible with the latest measurements) and a relatively high non-standard interactions discrimination potential predicted for the Daya Bay experiment.
In the third research line entertaining namely the virtues of the bottom-up approach to the extended gauge symmetries and grand unification, a special attention was paid namely to the fine correlations between the high-energy inputs governing the structure of the unified theories and the low-energy data and, in particular, the consistency and precision of the theoretical methods behind. Given the fellows expertise in renormalisation and symmetry aspects of gauge theories the main efforts here were spent on the fine effects of the so-called kinetic mixing inherent to theories with multiple abelian symmetry factors in their gauge group and their consistent implementation in the high precision calculations. The most important result attained in this direction was presumably the finalisation of the fundamental project launched by S. Martin and M. Vaughn in early 1990's focusing on the complete calculation of the structure of the two-loop renormalisation group in softly broken supersymmetric gauge theories. The relevant study was based on an original method developed by the fellow exploiting a simple residual reparametrisation invariance of a general gauge theory which provided a relatively straightforward recipe for generalising the existing results valid for utmost one U(1) gauge factor to the case of an arbitrary gauge group.
In conclusion, the project contributed significantly to the field of precision beyond Standard-Model physics by providing several highly interesting original result as well as new methods within its classical subjects such as grand unification and other extended gauge symmetries with a clear potential impact on developing a better understanding of the interplay among physics at vastly different energy scales. This, in turn, can shed more light on some of the fundamental questions about the origin and destiny of the Universe and the matter, radiation and other constituents within.
The results obtained so far are covered in the following peer-reviewed publications:
- Physical Review D83, 035002 (2011),
- Physical Review D83, 035018 (2011)
- Journal of High Energy Physics 12, 001 (2011),
- Physical Review D84, 053012 (2011),
- Nuclear Physics B854, 28 (2012),
- Journal of High Energy Physics 02, 084 (2012),
- Physical Review D85, 095014 (2012)
together with a couple of proceedings contributions:
- Journal of Physics: Conference Series 259 (2010) 012098,
- AIP Conference Proceedings 1467, 37 (2012).
Further information on the project execution is available at the dedicated website: http://www-ucjf.troja.mff.cuni.cz/~malinsky/fluent
The current fellow's affiliation is: Institute of Particle and Nuclear Physics
Faculty of Mathematics and Physics of the Charles University in Prague
V Holesovickach 2, 180 00 Praha 8, Czech Republic
Email: malinsky@ipnp.troja.mff.cuni.cz
Phone: +42-022-1912438