Search for New Physics with High Mass Tau Pairs in CDF Run II

2005 ◽  
Vol 20 (15) ◽  
pp. 3287-3289
Author(s):  
Zongru Wan
Keyword(s):  
Higgs Boson ◽  
Cross Section ◽  
Branching Ratio ◽  
New Physics ◽  
Mass Region ◽  
High Mass ◽  
Significant Excess ◽  
Upper Limits ◽  
Tau Pairs ◽  
Low Mass

We present the results of a search for new particles decaying to tau pairs. Hypothetical particles, such as Z′ and MSSM Higgs boson A can potentially produce such pairs. The low-mass region, dominated by Z → ττ, is used as a control. No significant excess events over the estimated backgrounds is observed in the high-mass region, and we set upper limits on the cross section times branching ratio as a function of the Z′ and A mass.

scholarly journals Search for exotic decays of the Higgs boson into long-lived particles in pp collisions at $$ \sqrt{s} $$ = 13 TeV using displaced vertices in the ATLAS inner detector

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Branching Ratio ◽  
High Mass ◽  
Proton Collision ◽  
Proton Proton ◽  
Upper Limits ◽  
Stringent Constraint ◽  
Model Predictions ◽  
Proton Proton Collision

Abstract A novel search for exotic decays of the Higgs boson into pairs of long-lived neutral particles, each decaying into a bottom quark pair, is performed using 139 fb−1 of $$ \sqrt{s} $$ s = 13 TeV proton-proton collision data collected with the ATLAS detector at the LHC. Events consistent with the production of a Higgs boson in association with a leptonically decaying Z boson are analysed. Long-lived particle (LLP) decays are reconstructed from inner-detector tracks as displaced vertices with high mass and track multiplicity relative to Standard Model processes. The analysis selection requires the presence of at least two displaced vertices, effectively suppressing Standard Model backgrounds. The residual background contribution is estimated using a data-driven technique. No excess over Standard Model predictions is observed, and upper limits are set on the branching ratio of the Higgs boson to LLPs. Branching ratios above 10% are excluded at 95% confidence level for LLP mean proper lifetimes cτ as small as 4 mm and as large as 100 mm. For LLP masses below 40 GeV, these results represent the most stringent constraint in this lifetime regime.

scholarly journals Search for lepton flavour violating muon decay mediated by a new light particle in the MEG experiment

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
A. M. Baldini ◽  
F. Berg ◽  
M. Biasotti ◽  
G. Boca ◽  
P. W. Cattaneo ◽  
...  
Keyword(s):  
Confidence Level ◽  
Branching Ratio ◽  
Mass Region ◽  
Muon Decay ◽  
Light Particle ◽  
Significant Excess ◽  
Upper Limits ◽  
Paul Scherrer ◽  
O 10 ◽  
Lepton Flavour

AbstractWe present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $$\upmu ^+ \rightarrow \mathrm {e}^+\mathrm {X}, \mathrm {X} \rightarrow \upgamma \upgamma \ $$ μ + → e + X , X → γ γ . This search uses a dataset resulting from $$7.5\times 10^{14}$$ 7.5 × 10 14 stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c$$^2$$ 2 for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c$$^2$$ 2 , down to $${\mathcal {O}}(10^{-11})$$ O ( 10 - 11 ) at 90% confidence level.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

scholarly journals D 2 O and HDS in the coma of 67P/Churyumov–Gerasimenko

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160253 ◽  
Author(s):  
K. Altwegg ◽  
H. Balsiger ◽  
J. J. Berthelier ◽  
A. Bieler ◽  
U. Calmonte ◽  
...  
Keyword(s):  
High Ratio ◽  
High Mass ◽  
Mass Star ◽  
Deuterated Water ◽  
Star Forming ◽  
Star Forming Regions ◽  
Upper Limits ◽  
Rosetta Mission ◽  
Low Mass ◽  
Grain Surface

The European Rosetta mission has been following comet 67P/Churyumov–Gerasimenko for 2 years, studying the nucleus and coma in great detail. For most of these 2 years the Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA) has analysed the volatile part of the coma. With its high mass resolution and sensitivity it was able to not only detect deuterated water HDO, but also doubly deuterated water, D 2 O and deuterated hydrogen sulfide HDS. The ratios for [HDO]/[H 2 O], [D 2 O]/[HDO] and [HDS]/[H 2 S] derived from our measurements are (1.05 ± 0.14) × 10 −3 , (1.80 ± 0.9) × 10 −2 and (1.2 ± 0.3) × 10 −3 , respectively. These results yield a very high ratio of 17 for [D 2 O]/[HDO] relative to [HDO]/[H 2 O]. Statistically one would expect just 1/4. Such a high value can be explained by cometary water coming unprocessed from the presolar cloud, where water is formed on grains, leading to high deuterium fractionation. The high [HDS]/[H 2 S] ratio is compatible with upper limits determined in low-mass star-forming regions and also points to a direct correlation of cometary H 2 S with presolar grain surface chemistry. This article is part of the themed issue ‘Cometary science after Rosetta’.

scholarly journals Higgs boson production cross-section measurements and their EFT interpretation in the $$4\ell $$ decay channel at $$\sqrt{s}=$$13 TeV with the ATLAS detector

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Cross Section ◽  
Decay Channel ◽  
Branching Ratio ◽  
Proton Collision ◽  
Boson Production ◽  
Theory Approach ◽  
Higgs Boson Production ◽  
The Standard Model

AbstractHiggs boson properties are studied in the four-lepton decay channel (where lepton = e, $$\mu $$ μ ) using 139 $$\hbox {fb}^{-1}$$ fb - 1 of proton–proton collision data recorded at $$\sqrt{s}=$$ s = 13 TeV by the ATLAS experiment at the Large Hadron Collider. The inclusive cross-section times branching ratio for $$H\rightarrow ZZ^*$$ H → Z Z ∗ decay is measured to be $$1.34 \pm 0.12$$ 1.34 ± 0.12  pb for a Higgs boson with absolute rapidity below 2.5, in good agreement with the Standard Model prediction of $$1.33 \pm 0.08$$ 1.33 ± 0.08  pb. Cross-sections times branching ratio are measured for the main Higgs boson production modes in several exclusive phase-space regions. The measurements are interpreted in terms of coupling modifiers and of the tensor structure of Higgs boson interactions using an effective field theory approach. Exclusion limits are set on the CP-even and CP-odd ‘beyond the Standard Model’ couplings of the Higgs boson to vector bosons, gluons and top quarks.

scholarly journals Charged Higgs bosons in the NMSSM under current LHC constraints

2019 ◽  
Vol 34 (28) ◽  
pp. 1950230
Author(s):  
Zhaoxia Heng ◽  
Lin Guo ◽  
Pengqiang Sun ◽  
Wei Wei
Keyword(s):  
Higgs Boson ◽  
Parameter Space ◽  
Branching Ratio ◽  
New Physics ◽  
Direct Search ◽  
Charged Higgs Boson ◽  
Higgs Bosons ◽  
Charged Higgs ◽  
Charged Higgs Bosons ◽  
The Masses

Charged Higgs boson is a crucial prediction of new physics beyond the SM. In this work, we perform a comprehensive scan over the parameter space of NMSSM considering various experimental constraints including the direct search limits from the 13 TeV LHC, and consider the scenario that the next-to-lightest CP-even Higgs boson is SM-like. We find that the masses of charged Higgs bosons can be as light as 350 GeV, the lightest CP-even Higgs boson [Formula: see text] is predominantly singlet and can be as light as 48 GeV, and the lightest CP-odd Higgs boson [Formula: see text] is also singlet-dominated and can be as light as 82 GeV. The charged Higgs bosons mainly decay to [Formula: see text] or [Formula: see text], but the branching ratio of the exotic decays [Formula: see text] and [Formula: see text] can maximally reach 20% and 11%, respectively, which can be used to distinguish the NMSSM from MSSM. Such a heavy charged Higgs boson is inaccessible at the 13 TeV LHC with a luminosity of 36.1 fb[Formula: see text] and its detection needs higher energy and/or higher luminosity.

scholarly journals Search for New Physics Using High-Mass Tau Pairs from 1.96 TeVpp¯Collisions

2005 ◽  
Vol 95 (13) ◽  
Author(s):  
D. Acosta ◽  
J. Adelman ◽  
T. Affolder ◽  
T. Akimoto ◽  
M. G. Albrow ◽  
...  
Keyword(s):  
New Physics ◽  
High Mass ◽  
Tau Pairs

J/ψ DECAYS AND η-η′-ι MIXING

1994 ◽  
Vol 09 (31) ◽  
pp. 5489-5506 ◽  
Author(s):  
ICHIJIRO KITAMURA ◽  
NORIKAZU MORISITA ◽  
TADAYUKI TESHIMA
Keyword(s):  
Experimental Data ◽  
Perturbation Theory ◽  
Mass Region ◽  
High Mass ◽  
Radial Excitation ◽  
Recent Experimental Data ◽  
Chiral Perturbation ◽  
Pseudoscalar Mesons ◽  
Low Mass ◽  
Excitation State

The mass region near η(1440) has more than one resonance, and two resonances with M≈1420 MeV and M≈1490 MeV are shown to give a better description of the recent experimental data. We investigate whether η(1420) or η(1490) is the glueball, if it exists, and which of them is the isospin 0 partner of the radially excited state η(1295) expected to exist near the 1500–1600 MeV region. We study the J/ψ→VP and Pγ decays, using the new data of 1992, to estimate the mixing among (η, η′, ι), where ι refers to the glueball, and obtain the result that the N component in ι is larger than the S component. Comparing the N and S components in ι with the N and S components in η(1420) and η(1490) obtained from their decaying pattern, we conjecture that the low mass state η(1420) is the glueball and the high mass state η(1490) is the radial excitation state. We discuss the relation between the mass formulae for the pseudoscalar mesons and the mixing among (η, η′, ι) obtained considering the chiral perturbation theory and the chiral U(3) × U(3) symmetry formulation.

scholarly journals Search for new non-resonant phenomena in high-mass dilepton final states with the ATLAS detector

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Contact Interaction ◽  
Hadron Collider ◽  
Mass Range ◽  
New Physics ◽  
Mass Region ◽  
Mass Scale ◽  
Energy Scale ◽  
High Mass ◽  
Final States ◽  
Dilepton Final States

Abstract A search for new physics with non-resonant signals in dielectron and dimuon final states in the mass range above 2 TeV is presented. This is the first search for non-resonant signals in dilepton final states at the LHC to use a background estimate from the data. The data, corresponding to an integrated luminosity of 139 fb−1, were recorded by the ATLAS experiment in proton-proton collisions at a center-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV during Run 2 of the Large Hadron Collider. The benchmark signal signature is a two-quark and two-lepton contact interaction, which would enhance the dilepton event rate at the TeV mass scale. To model the contribution from background processes a functional form is fit to the dilepton invariant-mass spectra in data in a mass region below the region of interest. It is then extrapolated to a high-mass signal region to obtain the expected background there. No significant deviation from the expected background is observed in the data. Upper limits at 95% CL on the number of events and the visible cross-section times branching fraction for processes involving new physics are provided. Observed (expected) 95% CL lower limits on the contact interaction energy scale reach 35.8 (37.6) TeV.

scholarly journals HIGGS SEARCHES AT THE TEVATRON

2010 ◽  
Vol 25 (27n28) ◽  
pp. 5097-5104
Author(s):  
◽  
KAZUHIRO YAMAMOTO
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Cross Section ◽  
Mass Range ◽  
Higgs Bosons ◽  
Beyond The Standard Model ◽  
Standard Model Higgs Boson ◽  
Significant Excess ◽  
Proton Antiproton ◽  
The Standard Model

We present the latest results on searches for the standard and beyond-the-standard model Higgs bosons in proton-antiproton collisions at [Formula: see text] by the CDF and DØ experiments at the Fermilab Tevatron. No significant excess is observed above the expected background, and the cross section limits for the Higgs bosons are calculated. It is noticed that the standard model Higgs boson in the mass range 163 – 166 GeV/c2 is excluded at the 95% C.L.

Sign in / Sign up

Export Citation Format

Share Document