22 results on '"Shafi, Qaisar"'
Search Results
2. Type III seesaw with R-parity violation in light of mW (CDF)
- Author
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Ghoshal, Anish, Okada, Nobuchika, Okada, Satomi, Raut, Digesh, Shafi, Qaisar, and Thapa, Anil
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- 2023
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3. Composite topological structures in SO(10)
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Lazarides, George, Shafi, Qaisar, and Tiwari, Amit
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- 2023
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- View/download PDF
4. Axions, WIMPs, proton decay and observable r in SO(10)
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Okada, Nobuchika, Raut, Digesh, and Shafi, Qaisar
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- 2023
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5. Light Z′B-L and Dirac fermion dark matter in the Z′B-L model
- Author
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Nath, Newton, Okada, Nobuchika, Okada, Satomi, Raut, Digesh, and Shafi, Qaisar
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- 2022
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- View/download PDF
6. Monopoles, exotic states and muon g-2 in TeV scale trinification
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Raut, Digesh, Shafi, Qaisar, and Thapa, Anil
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- 2022
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- View/download PDF
7. Muon g-2, neutralino dark matter and stau NLSP
- Author
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Gómez, Mario E., Shafi, Qaisar, Tiwari, Amit, and Ün, Cem Salih
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- 2022
- Full Text
- View/download PDF
8. Gravitational wave emission from metastable current-carrying strings in E6
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Afzal, Adeela, Shafi, Qaisar, and Tiwari, Amit
- Published
- 2024
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9. Cosmological probes of Grand Unification: Primordial Blackholes & scalar-induced Gravitational Waves
- Author
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Ghoshal, Anish, Moursy, Ahmad, and Shafi, Qaisar
- Subjects
High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,FOS: Physical sciences ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We investigate the inflationary cosmology involving an SU(5) GUT (grand unified theory) singlet scalar with non-minimal coupling to the Ricci scalar. In this scenario the scale of grand unification is set by the inflaton vev when the inflaton rolls down its potential towards its minimum $v$, thereby relating inflationary dynamics to GUT symmetry breaking with a prediction $r \simeq 0.025$ for the tensor-to-scalar ratio to be tested by the next generation CMB experiments. We show in this inflationary framework involving inflection-point how a suitable choice of parameters in $SU(5)$ leads to a bump in the scalar power spectrum with production of Primordial Blackholes (PBH) of masses $10^{17}-10^{18}$g ($ 10 - 100 M_\odot$). We derive the constraints on the self quartic and mixed quartic couplings of the inflaton in SU(5) that are consistent with the inflationary analysis. Moreover, we also show that this scenario leads to large amplitude induced second-order tensor perturbations propagating as Gravitational Waves (GW) with amplitude $\Omega_{\rm GW}h^2 \sim 10^{-17}$ and peak frequency $f_{\rm peak} \sim$ (0.1 - 1) Hz, which can be detected in the next generation GW observatories like LISA, BBO, ET, etc. Thus, we unify the $SU(5)$ framework with PBH via inflection-point inflation showing how the upcoming measurements of PBH and GW will enable us to probe the scale of $SU(5)$ symmetry breaking, and thereby complementing the laboratory based experiments. We also discuss scenarios involving the Pati-Salam and Trinification gauge groups and its impact on quartic and mixed-quartic couplings that may lead to PBH and detectable GW signals., Comment: In the revised version any inadvertent text overlap with other papers has been removed, the appendix is removed, and previous sections 5 and 6 have been merged. All results including figures and conclusions remain intact
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- 2023
10. Gravitational waves from walls bounded by strings in SO(10) model of pseudo-Goldstone dark matter
- Author
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Maji, Rinku, Park, Wan-Il, and Shafi, Qaisar
- Published
- 2023
- Full Text
- View/download PDF
11. Third family quasi-Yukawa unification: Higgsino dark matter, NLSP gluino and all that
- Author
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Shafi, Qaisar, Tiwari, Amit, and Un, Cem Salih
- Subjects
High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,FOS: Physical sciences - Abstract
We explore the implications of third family ($t-b-\tau$) quasi-Yukawa unification (QYU) for collider and dark matter (DM) searches within the framework of a supersymmetric $SU(4)_c \times SU(2)_L \times SU(2)_R$ model. The deviation from exact Yukawa unification is quantified through the relation $y_t : y_b : y_\tau = |1+C|:|1-C|:|1+3C|$, with $C$ being a real parameter ($|C| \leq 0.2$). We allow for the breaking of left-right symmetry both by the soft scalar and gaugino mass parameters and obtain a variety of viable solutions that predict the sparticle mass spectrum including LSP DM (whose stability is guaranteed by a $Z_2$ gauge symmetry). We highlight solutions that include an NLSP gluino with mass $\sim$ 1.3-2.5 TeV, which should be accessible at LHC Run 3. There also exist NSLP stop solutions with masses heavier than about 1.8 TeV, which are consistent with the LSP neutralino dark matter relic density through stop-neutralino coannihilation. We identify A-resonance solutions with DM mass $\sim$ 0.8 - 2 TeV, as well as bino-chargino, bino-slepton and bino-stau co-annihilation scenarios. Finally, we also identify Wino-like ($\sim99\%$) and Higgsino-like ($\sim99\%$) solutions whose masses are heavier than about 1.5 TeV and 1 TeV, respectively. These solutions are compatible with the desired dark matter relic density and testable in ongoing and future direct detection experiments., Comment: The revised draft includes Higgsino dark matter solutions and other improvements. Neutralino mixing and RGE evolutions of Yukawa couplings are corrected
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- 2023
12. Light $$Z^\prime $$ <math> <msup> <mi>Z</mi> <mo>′</mo> </msup> </math> and Dirac fermion dark matter in the $$B-L$$ <math> <mrow> <mi>B</mi> <mo>-</mo> <mi>L</mi> </mrow> </math> model
- Author
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Nath, Newton, Okada, Nobuchika, Okada, Satomi, Raut, Digesh, and Shafi, Qaisar
- Subjects
High Energy Physics - Experiment (hep-ex) ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Physics and Astronomy (miscellaneous) ,FOS: Physical sciences ,Engineering (miscellaneous) ,High Energy Physics - Experiment - Abstract
We consider a $U(1)_{B-L}$ model with a $Z^\prime$ portal Dirac fermion dark matter (DM) $\chi$ of low mass which couples very weakly to the $B - L$ gauge boson $Z^\prime$. An arbitrary $B-L$ charge $Q\neq \pm1, \pm 3$ of the DM $\chi$ ensures its stability. Motivated by the sensitivity reach of forthcoming "Lifetime Frontier" experiments, we focus on the $Z^\prime$ mass, $m_{Z^\prime}$, in the sub-GeV to few GeV range. To evaluate the DM relic abundance, we examine both the freeze-out and freeze-in DM scenarios. For the freeze-out scenario, we show that the observed DM abundance is reproduced near the $Z^\prime$ resonance, $m_\chi \simeq m_{Z^\prime}/2$, where $m_\chi$ is the DM mass. For the freeze-in scenario, we focus on $m_\chi \ll m_{Z^\prime}$. We show that for a fixed value of $m_{Z^\prime}$, $g_{BL}$ values roughly scale as $1/Q$ to reproduce the observed DM abundance. For various $Q$ values in the range between $10^{-6}$ and $10^2$, we show that the gauge coupling values $g_{BL}$ needed to reproduce the observed DM abundance lie in the search reach of future planned and/or proposed experiments such as FASER, Belle-II, LDMX, and SHiP. In the freeze-in case, the $Q$ values to realize observable $g_{BL}$ values are found to be much smaller than that in the freeze-out case., Comment: 14 pages, 3 figures, revised section III with new Figure 1
- Published
- 2022
13. Monopoles, exotic states and muon $$g-2$$ <math> <mrow> <mi>g</mi> <mo>-</mo> <mn>2</mn> </mrow> </math> in TeV scale trinification
- Author
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Raut, Digesh, Shafi, Qaisar, and Thapa, Anil
- Abstract
We study the low energy implications of a trinification model based on the gauge symmetry $$G= SU(3)_c \times SU(3)_L \times SU(3)_R$$ G = S U ( 3 ) c × S U ( 3 ) L × S U ( 3 ) R , without imposing gauge coupling unification. A minimal model requires two Higgs multiplets that reside in the bi-fundamental representation of G, and this is shown to be adequate for accommodating the Standard Model (SM) fermion masses and generate, via loop corrections and seesaw mechanism, suitable masses for the heavy neutral leptons as well as the observed SM neutrinos. We estimate a lower bound of around 15 TeV for the masses of the new down- type quarks that are required by the $$SU(3)_L \times SU(3)_R$$ S U ( 3 ) L × S U ( 3 ) R symmetry. We examine the resonant production at the LHC of the new gauge bosons, which leads to a lower bound of 16 TeV for the symmetry breaking scale of G. We also show how the muon $$g-2$$ g - 2 anomaly can be resolved in the presence of these new gauge bosons and the heavy charged leptons present in the model. Finally, the model predicts the presence of a topologically stable monopole carrying three quanta $$(6 \pi /e)$$ ( 6 π / e ) of Dirac magnetic charge and mass $$\gtrsim 160$$ ≳ 160 TeV. If new matter fields lying in the fundamental representations of G are included, the model predicts the presence of exotic leptons, mesons and baryons carrying fractional electric charges such as $$\pm e/3$$ ± e / 3 and $$\pm 2e/3$$ ± 2 e / 3 , fully compatible with the Dirac quantization condition.
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- 2022
14. Muon $$\mathbf {g-2}$$ <math> <mrow> <mi>g</mi> <mo>-</mo> <mn>2</mn> </mrow> </math> , neutralino dark matter and stau NLSP
- Author
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Gómez, Mario, Shafi, Qaisar, Tiwari, Amit, and Ün, Cem
- Abstract
We explore the implications of resolving the muon $$g-2$$ g - 2 anomaly in a $$SU(4)_c \times SU(2)_L \times SU(2)_R$$ S U ( 4 ) c × S U ( 2 ) L × S U ( 2 ) R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2 $$\sigma $$ σ resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass $$m_{\tilde{\tau }}\lesssim 400$$ m τ ~ ≲ 400 GeV, and the sleptons from the first two families can be as heavy as about 800 GeV. The chargino is also required to be lighter than about 600 GeV to accommodate the muon $$g-2$$ g - 2 solutions consistent with the dark matter relic density constraint. The dominant right-handed nature of the light slepton states suppress the sensitivity of possible signals which can be probed in Run3 experiments at the LHC. We also discuss the impact of accommodating the Higgs boson mass and the vacuum stability of the scalar potential for these solutions. Although a light stau can be compatible with the stability of the scalar potential, the Higgs boson mass constraint has a strong impact on the solutions with $$\tan \beta $$ tan β bounded from above, namely $$\tan \beta \lesssim 20$$ tan β ≲ 20 . The Higgsinos are heavier than about 4 TeV, and the LSP neutralino has the correct relic density if it is Bino-like. We identify stau–neutralino coannihilation as the dominant mechanism for realizing the desired dark matter relic density, with sneutrino–neutralino coannihiliation playing a minor role. These bino-like dark matter solutions can yield a spin-independent scattering cross-section on the order of $$10^{-13}$$ 10 - 13 pb which hopefully, can be expected to be tested in the near future.
- Published
- 2022
15. Monopoles, strings and gravitational waves in non-minimal inflation.
- Author
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Maji, Rinku and Shafi, Qaisar
- Published
- 2023
- Full Text
- View/download PDF
16. Muon g-2, Neutralino Dark Matter and Stau NLSP
- Author
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Gómez Santamaría, Mario Emilio, Shafi, Qaisar, Tiwari, Amit, and Ün, Cem Salih
- Subjects
High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,High Energy Physics::Experiment - Abstract
We explore the implications of resolving the muon g-2 anomaly in a SU(4)c×SU(2)L×SU(2)R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2s resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass mt~?400 GeV, and the sleptons from the first two families can be as heavy as about 800 GeV. The chargino is also required to be lighter than about 600 GeV to accommodate the muon g-2 solutions consistent with the dark matter relic density constraint. The dominant right-handed nature of the light slepton states suppress the sensitivity of possible signals which can be probed in Run3 experiments at the LHC. We also discuss the impact of accommodating the Higgs boson mass and the vacuum stability of the scalar potential for these solutions. Although a light stau can be compatible with the stability of the scalar potential, the Higgs boson mass constraint has a strong impact on the solutions with tanß bounded from above, namely tanß?20 . The Higgsinos are heavier than about 4 TeV, and the LSP neutralino has the correct relic density if it is Bino-like. We identify stau–neutralino coannihilation as the dominant mechanism for realizing the desired dark matter relic density, with sneutrino–neutralino coannihiliation playing a minor role. These bino-like dark matter solutions can yield a spin-independent scattering cross-section on the order of 10-13 pb which hopefully, can be expected to be tested in the near future., This work is supported in part by the United States Department of Energy grant DE-SC0013880 (QS and AT). The research of MEG and CSU is supported in part by the Spanish MICINN, under grant PID2019-107844GB-C22. We acknowledge Information Technologies (IT) resources at the University Of Delaware, specifically the high performance computing resources for the calculation of results presented in this paper
- Published
- 2022
17. <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>5</mn><mo>)</mo><mo>×</mo><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mi>X</mi></msub></math> axion model with observable proton decay
- Author
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Okada, Nobuchika, Raut, Digesh, and Shafi, Qaisar
- Abstract
We propose a SU(5)×U(1)X×U(1)PQ model, where U(1)X is the generalization of the B−L (baryon minus lepton number) gauge symmetry and U(1)PQ is the global Peccei-Quinn (PQ) symmetry. There are four fermions families in 5¯+10 representations of SU(5), a mirror family in 5+10¯ representations, and three SU(5) singlet Majorana fermions. The U(1)X related anomalies all cancel in the presence of the Majorana neutrinos. The SU(5) symmetry is broken at MGUT≃(6–9)×1015 GeV and the proton lifetime τp is estimated to be well within the expected sensitivity of the future hyper-Kamiokande experiment, τp≲1.3×1035 years. The SU(5) breaking also triggers the breaking of the PQ symmetry, resulting in axion dark matter (DM), with the axion decay constant fa of order MGUT or somewhat larger. The CASPEr experiment can search for such an axion DM candidate. The Hubble parameter during inflation must be low, Hinf≲109 GeV, in order to successfully resolve the axion domain wall, axion DM isocurvature and SU(5) monopole problems. With the identification of the U(1)X breaking Higgs field with the inflaton field, we implement inflection-point inflation, which is capable of realizing the desired value for Hinf. The vectorlike fermions in the model are essential for achieving successful unification of the SM gauge couplings as well as the phenomenological viability of both axion DM and inflation scenario.
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- 2021
18. Light Z′ and Dirac fermion dark matter in the B-L model.
- Author
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Nath, Newton, Okada, Nobuchika, Okada, Satomi, Raut, Digesh, and Shafi, Qaisar
- Subjects
DARK matter ,FERMIONS ,Z bosons ,GAUGE bosons - Abstract
We consider a U (1) B - L model with a Z ′ portal Dirac fermion dark matter (DM) χ of low mass which couples very weakly to the B - L gauge boson Z ′ . An arbitrary B - L charge Q ≠ ± 1 , ± 3 of the DM χ ensures its stability. Motivated by the sensitivity reach of forthcoming "Lifetime Frontier" experiments, we focus on the Z ′ mass, m Z ′ , in the sub-GeV to few GeV range. To evaluate the DM relic abundance, we examine both the freeze-out and freeze-in DM scenarios. For the freeze-out scenario, we show that the observed DM abundance is reproduced near the Z ′ resonance, m χ ≃ m Z ′ / 2 , where m χ is the DM mass. For the freeze-in scenario, we focus on m χ ≪ m Z ′ . We show that for a fixed value of m Z ′ , g BL values roughly scale as 1/Q to reproduce the observed DM abundance. For various Q values in the range between 10 - 6 and 10 2 , we show that the gauge coupling values g BL needed to reproduce the observed DM abundance lie in the search reach of future planned and/or proposed experiments such as FASER, Belle-II, LDMX, and SHiP. In the freeze-in case, the Q values to realize observable g BL values are found to be much smaller than that in the freeze-out case. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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19. Dirac plus Nambu monopoles in the Standard Model.
- Author
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Lazarides, George, Shafi, Qaisar, and Vachaspati, Tanmay
- Subjects
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STANDARD model (Nuclear physics) , *MAGNETIC flux , *MAGNETIC monopoles , *ELECTROWEAK interactions - Abstract
We show how in the standard electroweak model three SU(2)L Nambu monopoles, each carrying electromagnetic (EM) and Z magnetic fluxes, can merge (through Z strings) with a single U(1)Y Dirac monopole to yield a composite monopole that only carries EM magnetic flux. Compatibility with the Dirac quantization condition requires this composite monopole to carry six quanta (12π/e) of magnetic charge, independent of the electroweak mixing angle θw. The Dirac monopole is not regular at the origin and the energy of the composite monopole is therefore divergent. We discuss how this problem is cured by embedding U(1)Y in a grand unified group such as SU(5). A second composite configuration with only one Nambu monopole and a colored U(1)Y Dirac monopole that has minimal EM charge of 4π/e is also described. Finally, there exists a configuration with an EM charge of 8π/e as well as screened color magnetic charge. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
20. Pseudo-Goldstone dark matter in SO(10).
- Author
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Nobuchika Okada, Raut, Digesh, Shafi, Qaisar, and Thapa, Anil
- Subjects
- *
DARK matter , *LARGE Hadron Collider , *NAMBU-Goldstone bosons , *STANDARD model (Nuclear physics) , *SYMMETRY breaking , *MAGIC angle spinning - Abstract
We propose a pseudo-Goldstone boson dark matter (pGDM) particle in SO(10) grand unified theory (GUT). Due to its Goldstone nature, this pGDM evades the direct DM detection experiments which, otherwise, severely constrain the parameter space of DM models. In SO(10), the pGDM is embedded as a linear combination of the Standard Model (SM) singlet scalars in 16H and ̅126H representations. We consider two scenarios for the intermediate route of SO(10) symmetry breaking (SB) to the SM: SU(5)×U(1)X and Pati-Salam the SU(4)c×SU(2)L×SU(2)R(4-2-2) gauge groups. The vacuum expectation value of ̅126H, which triggers the breaking of U(1)X and 4-2-2 symmetry in the two scenarios, respectively, determines the pGDM lifetime whose astrophysical lower bound provides one of the most stringent constraints. For the 4-2-2 route to SO(10), the successful SM gauge coupling unification requires the 4-2-2 breaking scale to be O(1011) GeV, and most of the parameter space is excluded. For the SU(5)×U(1)X route, on the other hand, the U(1)X breaking scale can be significantly higher, and a wide range of the parameter space is allowed. Furthermore, the proton lifetime in the SU(5) case is predicted to be 4.53×1034 years, which lies well within the sensitivity reach of the Hyper-Kamiokande experiment. We also examine the constraints on the model parameter space from the Large Hadron Collider and the indirect DM search by Fermi-LAT and MAGIC experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
21. Cosmic strings, inflation, and gravity waves.
- Author
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Lazarides, George, Maji, Rinku, and Shafi, Qaisar
- Subjects
- *
GRAVITY waves , *COSMIC strings , *INFLATIONARY universe , *PRICE inflation , *COSMIC rays , *GRAVITATIONAL waves - Abstract
We investigate the impact of Coleman-Weinberg inflation on the stochastic gravity wave background spectrum emitted by intermediate-scale cosmic strings. The string network is partially inflated and reenters the horizon at later times after the end of inflation, such that the short string loops are not produced. This leads to a significant modification of the gravity wave spectrum that we explore in detail. We find that Coleman-Weinberg inflation can help to satisfy the Parkes Pulsar Timing Array (PPTA) bound for dimensionless string tension values in the range Gμ1.1×10-10. We also identify the modified gravity wave spectra which, in the case of inflation, are compatible with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) data. We then discuss the formation of monopoles and strings at the same breaking scale and the compatibility of the Monopole, Astrophysics and Cosmic Ray Observatory (MACRO) bound with the PPTA bound, and also with the NANOGrav data. Finally, an example of a realistic nonsupersymmetric E6 model incorporating successful Coleman-Weinberg inflation is presented in which monopoles and strings both survive inflation and are present at an observable level. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
22. SU(5)×U(1)X axion model with observable proton decay.
- Author
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Nobuchika Okada, Raut, Digesh, and Shafi, Qaisar
- Subjects
- *
AXIONS , *PROTON decay , *LEPTON number , *MAJORANA fermions , *DECAY constants , *HUBBLE constant - Abstract
We propose a SU(5)×U(1)X×U(1)PQ model, where U(1)X is the generalization of the B-L (baryon minus lepton number) gauge symmetry and U(1)PQ is the global Peccei-Quinn (PQ) symmetry. There are four fermions families in ¯5+10 representations of SU(5), a mirror family in 5+10 representations, and three SU(5) singlet Majorana fermions. The U(1)X related anomalies all cancel in the presence of the Majorana neutrinos. The SU(5) symmetry is broken at MGUT≃(6-9)×1015 GeV and the proton lifetime τp is estimated to be well within the expected sensitivity of the future hyper-Kamiokande experiment, τp≲1.3×1035 years. The SU(5) breaking also triggers the breaking of the PQ symmetry, resulting in axion dark matter (DM), with the axion decay constant fa of order MGUT or somewhat larger. The CASPEr experiment can search for such an axion DM candidate. The Hubble parameter during inflation must be low, Hinf≲109 GeV, in order to successfully resolve the axion domain wall, axion DM isocurvature and SU(5) monopole problems. With the identification of the U(1)X breaking Higgs field with the inflaton field, we implement inflection-point inflation, which is capable of realizing the desired value for Hinf. The vectorlike fermions in the model are essential for achieving successful unification of the SM gauge couplings as well as the phenomenological viability of both axion DM and inflation scenario. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
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