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Publications (10 of 19) Show all publications
Chandak, K., Mandal, T. & Mitra, S. (2019). Hunting for scalar leptoquarks with boosted tops and light leptons. Physical Review D: covering particles, fields, gravitation, and cosmology, 100(7), Article ID 075019.
Open this publication in new window or tab >>Hunting for scalar leptoquarks with boosted tops and light leptons
2019 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 7, article id 075019Article in journal (Refereed) Published
Abstract [en]

The LHC search strategies for leptoquarks that couple dominantly to a top quark are different than for the ones that couple mostly to the light quarks. We consider charge 1/3 (phi(1)) and 5/3 (phi(5)) scalar leptoquarks that can decay to a top quark and a charged lepton (tl) giving rise to a resonance system of a boosted top and a high-p(T) lepton. We introduce simple phenomenological models suitable for bottom-up studies and explicitly map them to all possible scalar leptoquark models within the Buchmuller-Ruckl-Wyler classifications that can have the desired decays. We study pair and single productions of these leptoquarks. Contrary to the common perception, we find that the single production of top-philic leptoquarks phi = {phi(1), phi(5)} in association with a lepton and jets could be significant for order one phi tl coupling in certain scenarios. We propose a strategy of selecting events with at least one hadronic-top and two high-p(T) same flavor opposite sign leptons. This captures events from both pair and single productions. Our strategy can significantly enhance the LHC discovery potential especially in the high-mass region where single productions become more prominent. Our estimation shows that a scalar leptoquark as heavy as similar to 1.7 TeV can be discovered at the 14 TeV LHC with 3 ab(-1) of integrated luminosity in the tll + X channel for 100% branching ratio in the phi -> tl decay mode. However, in some scenarios, the discovery reach can increase beyond 2 TeV even though the branching ratio comes down to about 50%.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-396708 (URN)10.1103/PhysRevD.100.075019 (DOI)000491169300005 ()
Available from: 2019-11-08 Created: 2019-11-08 Last updated: 2019-11-08Bibliographically approved
Bhardwaj, A., Konar, P., Mandal, T. & Sadhukhan, S. (2019). Probing the inert doublet model using jet substructure with a multivariate analysis. Physical Review D: covering particles, fields, gravitation, and cosmology, 100(5), Article ID 055040.
Open this publication in new window or tab >>Probing the inert doublet model using jet substructure with a multivariate analysis
2019 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 5, article id 055040Article in journal (Refereed) Published
Abstract [en]

We explore the challenging but phenomenologically interesting hierarchical mass spectrum of the inert doublet model where relatively light dark matter along with much heavier scalar states can fully satisfy the constraints on the relic abundance and also fulfill other theoretical as well as collider and astrophysical bounds. To probe this region of parameter space at the LHC, we propose a signal process that combines up to two large radius boosted jets along with substantial missing transverse momentum. Aided by our intuitive signal selection, we capture a hybrid process where the di-fatjet signal is significantly enhanced by the mono-fatjet contribution with minimal effects on the SM di-fatjet background. Substantiated by the sizable mass difference between the scalars, these boosted jets, originally produced from the hadronic decay of massive vector bosons, still carry the inherent footprint of their root. These features implanted inside the jet substructure can provide additional handles to deal with a large background involving QCD jets. We adopt a multivariate analysis using a boosted decision tree to provide a robust mechanism to explore the hierarchical scenario, which would bring almost the entire available parameter space well within reach of the 14 TeV LHC runs with high luminosity.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-395831 (URN)10.1103/PhysRevD.100.055040 (DOI)000488261300007 ()
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically approved
Mandal, T., Mitra, S. & Raz, S. (2019). R-D(*) motivated S-1 leptoquark scenarios: Impact of interference on the exclusion limits from LHC data. Physical Review D: covering particles, fields, gravitation, and cosmology, 99(5), Article ID 055028.
Open this publication in new window or tab >>R-D(*) motivated S-1 leptoquark scenarios: Impact of interference on the exclusion limits from LHC data
2019 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 99, no 5, article id 055028Article in journal (Refereed) Published
Abstract [en]

Motivated by the persistent anomalies in the semileptonic B-meson decays, we investigate the competency of LHC data to constrain the R-D(*)-favored parameter space in a charge -1/3 scalar leptoquark (S-1) model. We consider some scenarios with one large free coupling to accommodate the R-D(*) anomalies. As a result, some of them dominantly yield nonresonant tau tau and tau nu events at the LHC through the t-channel S-1 exchange. So far, no experiment has searched for leptoquarks using these signatures and the relevant resonant leptoquark searches are yet to put any strong exclusion limit on the parameter space. We recast the latest tau tau and tau nu resonance search data to obtain new exclusion limits. The nonresonant processes strongly interfere (destructively in our case) with the Standard Model background and play the determining role in setting the exclusion limits. To obtain precise limits, we include non-negligible effects coming from the subdominant (resonant) pair and inclusive single leptoquark productions systematically in our analysis. To deal with large destructive interference, we make use of the transverse mass distributions from the experiments in our statistical analysis. In addition, we also recast the relevant direct search results to obtain the most stringent collider bounds on these scenarios to date. These are independent bounds and are competitive to other known bounds. Finally, we indicate how one can adopt these bounds to a wide class of models with S-1 that are proposed to accommodate the R-D(*) anomalies.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-381125 (URN)10.1103/PhysRevD.99.055028 (DOI)000461908100004 ()
Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-04-04Bibliographically approved
Benbrik, R., Bergeås Kuutmann, E., Franzosi, D. B., Ellajosyula, V., Enberg, R., Ferretti, G., . . . Panizzi, L. (2019). Signatures of vector-like top partners decaying into new neutral scalar or pseudoscalar bosons.
Open this publication in new window or tab >>Signatures of vector-like top partners decaying into new neutral scalar or pseudoscalar bosons
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2019 (English)In: Article in journal (Other academic) Epub ahead of print
Abstract [en]

We explore the phenomenology of models containing one Vector-Like Quark (VLQ), t′, which can decay into the Standard Model (SM) top quark, t, and a new spin-0 neutral boson, S, the latter being either a scalar or pseudoscalar state. We parametrise the underlying interactions in terms of a simplified model which enables us to capture possible Beyond the SM (BSM) scenarios. We discuss in particular three such scenarios: one where the SM state is supplemented by an additional scalar, one which builds upon a 2-Higgs Doublet Model (2HDM) framework and another which realises a Composite Higgs Model (CHM) through partial compositeness. Such exotic decays of the t′ can be competitive with decays into SM particles, leading to new possible discovery channels at the Large Hadron Collider (LHC). Assuming t′ pair production via strong interactions, we design signal regions optimised for one t′→St transition (while being inclusive on the other \bar{t'} decay, and vice versa), followed by the decay of S into the two very clean experimental signatures S→γγ and S→Z(→ℓ+ℓ−)γ. We perform a dedicated signal-to-background analysis in both channels, by using Monte Carlo (MC) event simulations modelling the dynamics from the proton-proton to the detector level. Under the assumption of BR(t′→St)=100%, we are therefore able to realistically quantify the sensitivity of the LHC to both the t′ and S masses, assuming both current and foreseen luminosities. This approach paves the way for the LHC experiments to surpass current VLQ search strategies based solely on t′ decays into SM bosons (W±,Z, h).

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-389895 (URN)
Available from: 2019-07-31 Created: 2019-07-31 Last updated: 2019-08-15Bibliographically approved
Danielsson, U., Enberg, R., Ingelman, G. & Mandal, T. (2019). Varying gauge couplings and collider phenomenology. Physical Review D. Particles and fields, 100(5), Article ID 055028.
Open this publication in new window or tab >>Varying gauge couplings and collider phenomenology
2019 (English)In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 100, no 5, article id 055028Article in journal (Refereed) Published
Abstract [en]

In this paper we investigate a natural extension of the Standard Model that involves varying coupling constants. This is a general expectation in any fundamental theory such as string theory, and there are good reasons for why new physics could appear at reachable energy scales. We investigate the collider phenomenology of models with varying gauge couplings where the variations are associated with real singlet scalar fields. We introduce three different heavy scalar fields that are responsible for the variations of the three gauge couplings of the Standard Model. This gives rise to many interesting collider signatures that we explore, resulting in exclusion limits based on the most recent LHC data, and predictions of the future discovery potential at the high-luminosity LHC.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics; Theoretical Physics
Identifiers
urn:nbn:se:uu:diva-384700 (URN)10.1103/PhysRevD.100.055028 (DOI)000486644000010 ()
Funder
Swedish Research Council, 2015-04814
Available from: 2019-06-07 Created: 2019-06-07 Last updated: 2019-10-31Bibliographically approved
Mandal, T. (2018). Exclusion Limits on a Scalar Decaying to Photons and Distinguishing Its Production Mechanisms. Advances in High Energy Physics, Article ID 9150617.
Open this publication in new window or tab >>Exclusion Limits on a Scalar Decaying to Photons and Distinguishing Its Production Mechanisms
2018 (English)In: Advances in High Energy Physics, ISSN 1687-7357, E-ISSN 1687-7365, article id 9150617Article in journal (Refereed) Published
Abstract [en]

LHCrun-II has a great potential to search for new resonances in the diphoton channel. Latest 13 TeV data already put stringent limits on the cross sections in the diphoton channel assuming the resonance is produced through the gluon-gluon fusion. Many beyond the Standard Model (SM) theories predict TeV-scale scalars, which copiously decay to diphotons. Apart from the gluon-gluon fusion production, these scalars can also be dominantly produced in other ways too at the LHC, namely, through the quark-quark fusion or the gauge boson fusions like the photon-photon, photon-Z, WW, or ZZ fusions. In this paper we use an effective field theory approach where a heavy scalar can be produced in various ways and recast the latest ATLAS diphoton resonance search to put model-independent limits on its mass and effective couplings to the SM particles. If a new scalar is discovered at the LHC, it would be very important to identify its production mechanism in order to probe the nature of the underlying theory. We show that combining various kinematic variables in a multivariate analysis can be very powerful to distinguish different production mechanisms from one another.

Place, publisher, year, edition, pages
HINDAWI LTD, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-343389 (URN)10.1155/2018/9150617 (DOI)000423046700001 ()
Funder
Swedish Research Council, 621-2011-5107, 2015-04814Carl Tryggers foundation , CTS-14:206
Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-02-28Bibliographically approved
Mandal, T., Ekstedt, A., Enberg, R., Ingelman, G. & Löfgren, J. (2018). Exclusion Limits on Minimal Anomaly Free U(1) Extensions of the Standard Model. In: Naimuddin, M (Ed.), XXII DAE HIGH ENERGY PHYSICS SYMPOSIUM: . Paper presented at 22nd DAE-BRNS High Energy Physics (HEP) Symposium, DEC 12-16, 2016, Univ Delhi, Dept Phys & Astrophys, New Delhi, INDIA (pp. 243-246). SPRINGER-VERLAG BERLIN
Open this publication in new window or tab >>Exclusion Limits on Minimal Anomaly Free U(1) Extensions of the Standard Model
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2018 (English)In: XXII DAE HIGH ENERGY PHYSICS SYMPOSIUM / [ed] Naimuddin, M, SPRINGER-VERLAG BERLIN , 2018, p. 243-246Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
SPRINGER-VERLAG BERLIN, 2018
Series
Springer Proceedings in Physics, ISSN 0930-8989, E-ISSN 1867-4941 ; 203
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-364847 (URN)10.1007/978-3-319-73171-1_55 (DOI)000442670100054 ()978-3-319-73171-1 (ISBN)978-3-319-73170-4 (ISBN)
Conference
22nd DAE-BRNS High Energy Physics (HEP) Symposium, DEC 12-16, 2016, Univ Delhi, Dept Phys & Astrophys, New Delhi, INDIA
Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2018-11-05Bibliographically approved
Camargo-Molina, J. E., Mandal, T., Pasechnik, R. & Wessen, J. (2018). Heavy charged scalars from cs̄ fusion: a generic search strategy applied to a 3HDM with U(1) x U(1) family symmetry. Journal of High Energy Physics (JHEP) (3), Article ID 024.
Open this publication in new window or tab >>Heavy charged scalars from cs̄ fusion: a generic search strategy applied to a 3HDM with U(1) x U(1) family symmetry
2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 3, article id 024Article in journal (Refereed) Published
Abstract [en]

We describe a class of three Higgs doublet models (3HDMs) with a softly broken U(1) x U(1) family symmetry that enforces a Cabibbo-like quark mixing while forbidding tree-level flavour changing neutral currents. The hierarchy in the observed quark masses is partly explained by a softer hierarchy in the vacuum expectation values of the three Higgs doublets. As a consequence, the physical scalar spectrum contains a Standard Model (SM) like Higgs boson h(125) while exotic scalars couple the strongest to the second quark family, leading to rather unconventional discovery channels that could be probed at the Large Hadron Collider. In particular, we describe a search strategy for the lightest charged Higgs boson H-+/-, through the process c -> H+ -> W+ h(125), using a multivariate analysis that leads to an excellent discriminatory power against the SM background. Although the analysis is applied to the proposed class of 3HDMs, we employ a model-independent formulation such that it can be applied to any other model with the same discovery channel.

Keywords
Beyond Standard Model, Higgs Physics, Quark Masses and SM Parameters
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-350631 (URN)10.1007/JHEP03(2018)024 (DOI)000426798800002 ()
Funder
Swedish Research Council, 621-2011-5107Swedish Research Council, 2015-04814Swedish Research Council, 621-2013-428Swedish Research Council, 2016-05996
Note

Title in WoS: Heavy charged scalars from c(s)over-bar fusion: a generic search strategy applied to a 3HDM with U(1) x U(1) family symmetry

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2018-05-21Bibliographically approved
Ekstedt, A., Enberg, R., Ingelman, G., Löfgren, J. & Mandal, T. (2018). Minimal anomalous U(1) theories and collider phenomenology. Journal of High Energy Physics (JHEP), 1802, 152
Open this publication in new window or tab >>Minimal anomalous U(1) theories and collider phenomenology
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2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 1802, p. 152-Article in journal (Refereed) Published
Abstract [en]

We study the collider phenomenology of a neutral gauge boson Z′ arising in minimal but anomalous U(1) extensions of the Standard Model (SM). To retain gauge invariance of physical observables, we consider cancellation of gauge anomalies through the Green-Schwarz mechanism. We categorize a wide class of U(1) extensions in terms of the new U(1) charges of the left-handed quarks and leptons and the Higgs doublet. We derive constraints on some benchmark models using electroweak precision constraints and the latest 13 TeV LHC dilepton and dijet resonance search data. We calculate the decay rates of the exotic and rare one-loop Z′ decays to ZZ and Z-photon modes, which are the unique signatures of our framework. If observed, these decays could hint at anomaly cancellation through the Green-Schwarz mechanism. We also discuss the possible observation of such signatures at the LHC and at future ILC colliders.

National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-336639 (URN)10.1007/JHEP02(2018)152 (DOI)000426358100007 ()
Funder
Carl Tryggers foundation , CTS-14:206Swedish Research Council, 621-2011-5107
Available from: 2017-12-15 Created: 2017-12-15 Last updated: 2019-05-13Bibliographically approved
Mandal, T. & Jaikumar, P. (2017). Effect of Strong Magnetic Field on Competing Order Parameters in Two-Flavor Dense Quark Matter. Advances in High Energy Physics, Article ID 6472909.
Open this publication in new window or tab >>Effect of Strong Magnetic Field on Competing Order Parameters in Two-Flavor Dense Quark Matter
2017 (English)In: Advances in High Energy Physics, ISSN 1687-7357, E-ISSN 1687-7365, article id 6472909Article in journal (Refereed) Published
Abstract [en]

We study the effect of strong magnetic field on competing chiral and diquark order parameters in a regime of moderately dense quarkmatter. Theinterdependence of the chiral and diquark condensates through nonperturbative quark mass and strong coupling effects is analyzed in a two-flavorNambu-Jona-Lasinio (NJL) model. In the weak magnetic field limit, our results agree qualitatively with earlier zero-field studies in the literature that find a critical coupling ratio G(D/)G(S) similar to 1.1 below which chiral or superconducting order parameters appear almost exclusively. Above the ratio, there exists a significant mixed broken phase region where both gaps are nonzero. However, a strongmagnetic field greater than or similar to 10(18)G disrupts this mixed broken phase region and changes a smooth crossover found in the weak-field case to a first-order transition for both gaps at almost the same critical density. Our results suggest that in the two-flavor approximation to moderately dense quark matter strong magnetic field enhances the possibility of a mixed phase at high density, with implications for the structure, energetics, and vibrational spectrum of neutron stars.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-319306 (URN)10.1155/2017/6472909 (DOI)000395155700001 ()
Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2017-11-29Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-7268-549X

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