Piyush Kumar - Academia.edu (original) (raw)
Papers by Piyush Kumar
Journal of High Energy Physics, 2009
We propose that the leptonic cosmic ray signals seen by PAMELA and ATIC result from the annihilat... more We propose that the leptonic cosmic ray signals seen by PAMELA and ATIC result from the annihilation or decay of dark matter particles via states of a leptonic Higgs doublet to τ leptons, linking cosmic ray signals of dark matter to LHC signals of the Higgs sector. The states of the leptonic Higgs doublet are lighter than about 200 GeV, yielding largeτ τ and τ ττ τ event rates at the LHC. Simple models are given for the dark matter particle and its interactions with the leptonic Higgs, for cosmic ray signals arising from both annihilations and decays in the galactic halo. For the case of annihilations, cosmic photon and neutrino signals are on the verge of discovery. Contents I. Introduction 2 II. The Higgs as a Messenger of Dark Matter Signals 4 III. The Leptonic Higgs Boson 6 IV. Astrophysics Signals 9 A. Positrons (& Electrons) B. Photons C. Neutrinos V. Higgs Physics-Collider Signals A. The Higgs Potential B. Potential Signals at the LHC 1. The Z * → HA →τ ττ τ Signal 2. The h, H →τ τ Signal 3. The h → HH, AA →τ ττ τ Signal VI. Some simple DM Models with Leptonic Higgs A. L − L c − N DM Model 1. Annihilating Dark Matter 2. Decaying Dark Matter B. Singlet Scalar DM Model C. Inert Higgs-Doublet DM Model VII. Conclusions and Summary Recent observations of high-energy electron and positron cosmic ray spectra have generated tremendous interest, as they might provide the first non-gravitational evidence for Dark Matter (DM). The PAMELA [1] experiment reports an excess of positrons in the few GeV to 100 GeV range, providing further support to the earlier results of HEAT [2] and AMS [3]. In addition, results from the ATIC [4] and PPB-BETS [5] balloon experiments suggest an excess of electrons and positrons in the 300 GeV to 600 GeV range. While these observations have conventional astrophysical interpretations, they may result from annihilations or decays of DM particles in the galactic halo. Indeed, the PAMELA and ATIC data reinforce each other, since, for a certain range of DM masses, they have a unified interpretation. However, DM
Journal of High Energy Physics, 2011
We consider a broad class of supersymmetric theories in which dark matter (DM) is the lightest su... more We consider a broad class of supersymmetric theories in which dark matter (DM) is the lightest superpartner (LSP) of a hidden sector that couples very weakly to visible sector fields. Portal interactions connecting visible and hidden sectors mediate the decay of the lightest observable superpartner (LOSP) into the LSP, allowing the LHC to function as a spectacular probe of the origin of hidden sector DM. As shown in a companion paper, this general two-sector framework allows only for a handful of DM production mechanisms, each of which maps to a distinctive window in lifetimes and cross-sections for the LOSP. In the present work we perform a systematic collider study of LOSP candidates and portal interactions, and for each case evaluate the prospects for successfully reconstructing the origin of DM at the LHC. If, for instance, DM arises from Freeze-Out and Decay, this may be verified if the LOSP is a bino or right-handed slepton decaying to the LSP through a variety of portal interactions, and with an annihilation cross-section within a narrow range. On the other hand, the Freeze-In mechanism may be verified for a complimentary set of LOSP candidates, and within a narrow range of LOSP lifetimes. In all cases, the LOSP is relatively long-lived on collider time scales, leading to events with displaced vertices. Furthermore, scenarios with a charged or colored LOSP are particularly promising.
Journal of High Energy Physics, 2011
We present a systematic cosmological study of a universe in which the visible sector is coupled, ... more We present a systematic cosmological study of a universe in which the visible sector is coupled, albeit very weakly, to a hidden sector comprised of its own set of particles and interactions. Assuming that dark matter (DM) resides in the hidden sector and is charged under a stabilizing symmetry shared by both sectors, we determine all possible origins of weak-scale DM allowed within this broad framework. We show that DM can arise only through a handful of mechanisms, lending particular focus to Freeze-Out and Decay and Freeze-In, as well as their variations involving late time re-annihilations of DM and DM particle anti-particle asymmetries. Much like standard Freeze-Out, where the abundance of DM depends only on the annihilation cross-section of the DM particle, these mechanisms depend only on a very small subset of physical parameters, many of which may be measured directly at the LHC. In particular, we show that each DM production mechanism is associated with a distinctive window in lifetimes and cross-sections for particles which may be produced in the near future. We evaluate prospects for employing the LHC to definitively reconstruct the origin of DM in a companion paper.
Physical Review D, 2010
We explore the possibility that both the weak scale and the thermal relic dark matter abundance a... more We explore the possibility that both the weak scale and the thermal relic dark matter abundance are environmentally selected in a multiverse. An underlying supersymmetric theory containing the states of the MSSM and singlets, with supersymmetry and R symmetry broken at unified scales, has just two realistic low energy effective theories. One theory, (SM +w), is the Standard Model augmented only by the wino, having a mass near 3 TeV, and has a Higgs boson mass in the range of (127-142) GeV. The other theory, (SM +h/s), has Higgsinos and a singlino added to the Standard Model. The Higgs boson mass depends on the single new Yukawa coupling of the theory, y, and is near 141 GeV for small y but grows to be as large as 210 GeV as this new coupling approaches strong coupling at high energies. Much of the parameter space of this theory will be probed by direct detection searches for dark matter that push two orders of magnitude below the present bounds; furthermore, the dark matter mass and cross section on nucleons are correlated with the Higgs boson mass. The indirect detection signal of monochromatic photons from the galactic center is computed, and the range of parameters that may be accessible to LHC searches for trilepton events is explored. Taking a broader view, allowing the possibility of R symmetry protection to the TeV scale or axion dark matter, we find four more theories: (SM + axion), two versions of Split Supersymmetry, and the E-MSSM, where a little supersymmetric hierarchy is predicted. The special Higgs mass value of (141 ± 2) GeV appears in symmetry limits of three of the six theories, (SM + axion), (SM +w) and (SM +h/s), motivating a comparison of other signals of these three theories.
Journal of High Energy Physics, 2009
We propose that the leptonic cosmic ray signals seen by PAMELA and ATIC result from the annihilat... more We propose that the leptonic cosmic ray signals seen by PAMELA and ATIC result from the annihilation or decay of dark matter particles via states of a leptonic Higgs doublet to τ leptons, linking cosmic ray signals of dark matter to LHC signals of the Higgs sector. The states of the leptonic Higgs doublet are lighter than about 200 GeV, yielding largeτ τ and τ ττ τ event rates at the LHC. Simple models are given for the dark matter particle and its interactions with the leptonic Higgs, for cosmic ray signals arising from both annihilations and decays in the galactic halo. For the case of annihilations, cosmic photon and neutrino signals are on the verge of discovery. Contents I. Introduction 2 II. The Higgs as a Messenger of Dark Matter Signals 4 III. The Leptonic Higgs Boson 6 IV. Astrophysics Signals 9 A. Positrons (& Electrons) B. Photons C. Neutrinos V. Higgs Physics-Collider Signals A. The Higgs Potential B. Potential Signals at the LHC 1. The Z * → HA →τ ττ τ Signal 2. The h, H →τ τ Signal 3. The h → HH, AA →τ ττ τ Signal VI. Some simple DM Models with Leptonic Higgs A. L − L c − N DM Model 1. Annihilating Dark Matter 2. Decaying Dark Matter B. Singlet Scalar DM Model C. Inert Higgs-Doublet DM Model VII. Conclusions and Summary Recent observations of high-energy electron and positron cosmic ray spectra have generated tremendous interest, as they might provide the first non-gravitational evidence for Dark Matter (DM). The PAMELA [1] experiment reports an excess of positrons in the few GeV to 100 GeV range, providing further support to the earlier results of HEAT [2] and AMS [3]. In addition, results from the ATIC [4] and PPB-BETS [5] balloon experiments suggest an excess of electrons and positrons in the 300 GeV to 600 GeV range. While these observations have conventional astrophysical interpretations, they may result from annihilations or decays of DM particles in the galactic halo. Indeed, the PAMELA and ATIC data reinforce each other, since, for a certain range of DM masses, they have a unified interpretation. However, DM
Journal of High Energy Physics, 2011
We consider a broad class of supersymmetric theories in which dark matter (DM) is the lightest su... more We consider a broad class of supersymmetric theories in which dark matter (DM) is the lightest superpartner (LSP) of a hidden sector that couples very weakly to visible sector fields. Portal interactions connecting visible and hidden sectors mediate the decay of the lightest observable superpartner (LOSP) into the LSP, allowing the LHC to function as a spectacular probe of the origin of hidden sector DM. As shown in a companion paper, this general two-sector framework allows only for a handful of DM production mechanisms, each of which maps to a distinctive window in lifetimes and cross-sections for the LOSP. In the present work we perform a systematic collider study of LOSP candidates and portal interactions, and for each case evaluate the prospects for successfully reconstructing the origin of DM at the LHC. If, for instance, DM arises from Freeze-Out and Decay, this may be verified if the LOSP is a bino or right-handed slepton decaying to the LSP through a variety of portal interactions, and with an annihilation cross-section within a narrow range. On the other hand, the Freeze-In mechanism may be verified for a complimentary set of LOSP candidates, and within a narrow range of LOSP lifetimes. In all cases, the LOSP is relatively long-lived on collider time scales, leading to events with displaced vertices. Furthermore, scenarios with a charged or colored LOSP are particularly promising.
Journal of High Energy Physics, 2011
We present a systematic cosmological study of a universe in which the visible sector is coupled, ... more We present a systematic cosmological study of a universe in which the visible sector is coupled, albeit very weakly, to a hidden sector comprised of its own set of particles and interactions. Assuming that dark matter (DM) resides in the hidden sector and is charged under a stabilizing symmetry shared by both sectors, we determine all possible origins of weak-scale DM allowed within this broad framework. We show that DM can arise only through a handful of mechanisms, lending particular focus to Freeze-Out and Decay and Freeze-In, as well as their variations involving late time re-annihilations of DM and DM particle anti-particle asymmetries. Much like standard Freeze-Out, where the abundance of DM depends only on the annihilation cross-section of the DM particle, these mechanisms depend only on a very small subset of physical parameters, many of which may be measured directly at the LHC. In particular, we show that each DM production mechanism is associated with a distinctive window in lifetimes and cross-sections for particles which may be produced in the near future. We evaluate prospects for employing the LHC to definitively reconstruct the origin of DM in a companion paper.
Physical Review D, 2010
We explore the possibility that both the weak scale and the thermal relic dark matter abundance a... more We explore the possibility that both the weak scale and the thermal relic dark matter abundance are environmentally selected in a multiverse. An underlying supersymmetric theory containing the states of the MSSM and singlets, with supersymmetry and R symmetry broken at unified scales, has just two realistic low energy effective theories. One theory, (SM +w), is the Standard Model augmented only by the wino, having a mass near 3 TeV, and has a Higgs boson mass in the range of (127-142) GeV. The other theory, (SM +h/s), has Higgsinos and a singlino added to the Standard Model. The Higgs boson mass depends on the single new Yukawa coupling of the theory, y, and is near 141 GeV for small y but grows to be as large as 210 GeV as this new coupling approaches strong coupling at high energies. Much of the parameter space of this theory will be probed by direct detection searches for dark matter that push two orders of magnitude below the present bounds; furthermore, the dark matter mass and cross section on nucleons are correlated with the Higgs boson mass. The indirect detection signal of monochromatic photons from the galactic center is computed, and the range of parameters that may be accessible to LHC searches for trilepton events is explored. Taking a broader view, allowing the possibility of R symmetry protection to the TeV scale or axion dark matter, we find four more theories: (SM + axion), two versions of Split Supersymmetry, and the E-MSSM, where a little supersymmetric hierarchy is predicted. The special Higgs mass value of (141 ± 2) GeV appears in symmetry limits of three of the six theories, (SM + axion), (SM +w) and (SM +h/s), motivating a comparison of other signals of these three theories.