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Dhamija, R. (ORCID:0000000170523163)

Publications and source records attributed to Dhamija, R. (ORCID:0000000170523163).

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Measurement of the ๐ท 0 โ†’๐พ โˆ’ โข๐œ‹ + โข๐‘’ + โข๐‘’ โˆ’ branching fraction and search for ๐ท 0 โ†’ ๐œ‹ + โข๐œ‹ โˆ’ โข๐‘’ + โข๐‘’ โˆ’ and ๐ท 0 โ†’๐พ + โข๐พ โˆ’ โข๐‘’ + โข๐‘’ โˆ’ decays at Belle

We present a study of the rare charm meson decays ๐ท 0 โ†’๐พ + โข๐พ โˆ’ โข๐‘’ + โข๐‘’ โˆ’ , ๐œ‹ + โข๐œ‹ โˆ’ โข๐‘’ + โข๐‘’ โˆ’ , and ๐พ โˆ’ โข๐œ‹ + โข๐‘’ + โข๐‘’ โˆ’ using a 942 fb โˆ’1 dataset collected by the Belle detector at the KEKB asymmetric-energy ๐‘’ + โข๐‘’ โˆ’ collider. We identify ๐ท 0 candidates via the charge of the pion from ๐ท* + โ†’๐ท 0 โข๐œ‹ + decays and normalize the branching fractions to ๐ท 0 โ†’ ๐พ โˆ’ โข๐œ‹ + โข๐œ‹ โˆ’ โข๐œ‹ + decays. The branching fraction for decay ๐ท 0 โ†’ ๐พ โˆ’ โข๐œ‹ + โข๐‘’ + โข๐‘’ โˆ’ is measured to be (39.6 ยฑ 4.5 (stat) ยฑ 2.9 (syst)) ร— 10 โˆ’7 , with the dielectron mass in the ๐œŒ/๐œ” mass region 675 < ๐‘š ๐‘’โข๐‘’ < 875 MeV/โข๐‘ 2 . We also search for ๐ท 0 โ†’ โ„Ž โˆ’ โกโ„Ž (โ€ฒ)+ โก๐‘’ + โข๐‘’ โˆ’ (โ„Ž (โ€ฒ) = ๐พ, ๐œ‹) decays with the dielectron mass near the ๐œ‚ and ๐œ™ resonances, and away from these resonances for the ๐พ + โข๐พ โˆ’ โข๐‘’ + โข๐‘’ โˆ’ and ๐œ‹ + โข๐œ‹ โˆ’ โข๐‘’ + โข๐‘’ โˆ’ modes. For these modes, we find no significant signals and set 90% confidence level upper limits on their branching fractions at the ๐’ชโก(10 โˆ’7 ) level.

branching fractionโ†—
DOE OSTI2025

Search for B 0 โ†’ K *0 ๐œ + โข๐œ โˆ’ Decays at the Belle II Experiment

We present a search for the rare flavor-changing neutral-current decay ๐ต 0 โ†’๐พ *0 โข๐œ + โข๐œ โˆ’ with data collected by the Belle II experiment at the SuperKEKB electron-positron collider. The analysis uses a 365 fb โˆ’1 data sample recorded at the center-of-mass energy of the ฯ’โก(4โข๐‘†) resonance. One of the ๐ต mesons produced in the ฯ’โก(4โข๐‘†)โ†’๐ต 0 $โข\overline{๐ต}$ 0 process is fully reconstructed in a hadronic decay mode, while its companion ๐ต meson is required to decay into a ๐พ *0 and two ๐œ leptons of opposite charge. The ๐œ leptons are reconstructed in final states with a single electron, muon, charged pion or charged ๐œŒ meson, and additional neutrinos. We set an upper limit on the branching fraction of โ„ฌโก(๐ต 0 โ†’๐พ *0 โข๐œ + โข๐œ โˆ’ )<1.8ร—10 โˆ’3 at the 90% confidence level, which is the most stringent constraint reported to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSโ†—
DOE OSTI2025

Test of lepton flavor universality with measurements of ๐‘…โก(๐ท + ) and ๐‘…โก(๐ท* + ) using semileptonic ๐ต tagging at the Belle II experiment

We report measurements of the ratios of branching fractions โ„›โก(๐ท (*)+ ) = โ„ฌโก($\bar{๐ต}$ 0 โ†’ ๐ท (*)+ โข๐œ โˆ’โข $\bar{๐œˆ}$ ๐œ )/โ„ฌโก($\bar{๐ต}$ 0 โ†’ ๐ท (*)+ โขโ„“ โˆ’ $\bar{๐œˆ}$ โ„“ ), where โ„“ denotes either an electron or a muon. These ratios test the universality of the charged-current weak interaction. The results are based on a 365 fb โˆ’1 data sample collected with the Belle II detector at the SuperKEKB ๐‘’ + โข๐‘’ โˆ’ collider, which operates at a center-of-mass energy corresponding to the ฯ’โก(4โข๐‘†) resonance, just above the threshold for $๐ต\bar{๐ต}$ production. Signal candidates are reconstructed by selecting events in which the companion ๐ต meson from the ฯ’โก(4โข๐‘†) โ†’ $๐ต\bar{๐ต}$ decay is identified in semileptonic modes. The ๐œ lepton is reconstructed via its leptonic decays. We obtain โ„›โก(๐ท + ) = 0.418$^{+0.075}_{โˆ’0.073}$โข(stat)$^{+0.049}_{โˆ’0.056}$โข(syst) and โ„›โก(๐ท *+ ) = 0.306$^{+0.035}_{โˆ’0.033}$โข(stat)$^{+0.016}_{โˆ’0.018โข}$(syst), which are consistent with world average values. Accounting for the correlation between them, these values differ from the Standard Model expectation by a collective significance of 1.7 standard deviations.

bottom quarkโ†—
DOE OSTI2025

Search for Lepton-Flavor-Violating Decay Modes ๐ต 0 โ†’๐พ$^0_๐‘†$โข๐œ ยฑ โขโ„“ โˆ“ with Hadronic ๐ต Tagging at Belle and Belle II

We present the first search for the lepton-flavor-violating decay modes ๐ต 0 โ†’๐พ$^0_๐‘†$โข๐œ ยฑ โขโ„“ โˆ“ (โ„“=๐œ‡,๐‘’) using the 711 and 365 fb โˆ’1 data samples recorded by the Belle and Belle II detectors, respectively. We use a hadronic ๐ต-tagging technique to fully reconstruct a ๐ต meson and search for signal decays in the system recoiling against the tagged meson, considering ๐œ decays to either light leptons, one charged hadron, or one charged hadron and a neutral pion. We find no evidence for ๐ต 0 โ†’๐พ$^0_๐‘†$โข๐œ ยฑ โขโ„“ โˆ“ decays and set 90% confidence level upper limits on the branching fractions in the range of [0.8,3.6] ร—10 โˆ’5 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSโ†—
DOE OSTI2025

Search for ๐‘ƒ ๐‘$\overline{๐‘}$๐‘  โข(4459) 0 and ๐‘ƒ ๐‘$\overline{๐‘}$๐‘  (4338) 0 in ฯ’(1๐‘†,2๐‘†) Inclusive Decays at Belle

Using data samples of 102 million ฯ’โก(1โข๐‘†) events and 158 million ฯ’โก(2โข๐‘†) events collected by the Belle detector at the KEKB asymmetric-energy ๐‘’+โข๐‘’โˆ’ collider, we search for [๐‘ขโข๐‘‘โข๐‘ โข๐‘$\overline{๐‘}$ ] pentaquark states decaying to ๐ฝ/๐œ“โขฮ›. Using the first observations of ฯ’โก(1โข๐‘†,2โข๐‘†) inclusive decays to ๐ฝ/๐œ“โขฮ›, we find evidence of the ๐‘ƒ ๐‘$\overline{๐‘}$๐‘  โข(4459) 0 state with a local significance of 3.3 standard deviations, including statistical and systematic uncertainties. We measure the mass and width of the ๐‘ƒ ๐‘$\overline{๐‘}$๐‘  โข(4459) 0 to be (4471.7ยฑ4.8ยฑ0.6) MeV/๐‘ 2 and (22 ยฑ13 ยฑ3) MeV, respectively. The branching fractions for ๐‘ƒ ๐‘$\overline{๐‘}$๐‘  โข(4459) 0 production are measured to be โ„ฌโก[ฯ’โก(1โข๐‘†)โ†’๐‘ƒ ๐‘$\overline{๐‘}$๐‘  โข(4459)0/ $\overline{๐‘ƒ}$ ๐‘$\overline{๐‘}$๐‘  โข(4459) 0 +anything]=(3.5ยฑ2.0ยฑ0.2)ร—10 โˆ’6 and โ„ฌโก[ฯ’โก(2โข๐‘†)โ†’๐‘ƒ ๐‘$\overline{๐‘}$๐‘  โข(4459) 0 /$\overline{๐‘ƒ}$ ๐‘$\overline{๐‘}$๐‘  โข(4459) 0 +anything]=(2.9ยฑ1.7ยฑ0.4)ร—10 โˆ’6 . The inclusive branching fractions of ฯ’โก(1โข๐‘†,2โข๐‘†) โ†’๐ฝ/๐œ“โขฮ›/$\overline{ฮ›}$ are measured to be โ„ฌโก[ฯ’โก(1โข๐‘†) โ†’๐ฝ/๐œ“โขฮ›/$\overline{ฮ›}$ +anything] =(36.9 ยฑ5.3 ยฑ2.4) ร—10 โˆ’6 and โ„ฌโก[ฯ’โก(2โข๐‘†) โ†’๐ฝ/๐œ“โขฮ›/$\overline{ฮ›}$ +anything] =(22.3 ยฑ5.7 ยฑ3.1) ร—10 โˆ’6 . We measure the visible cross section ๐œŽโก(๐‘’+โข๐‘’โˆ’โ†’๐ฝ/๐œ“โขฮ›/ $\overline{ฮ›}$ +anything)=(90ยฑ14ยฑ6) fb for the continuum production at โˆš๐‘  =10.52 GeV. In all cases, the first uncertainties are statistical and the second are systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSโ†—
DOE OSTI2025

Measurement of the branching fraction of ฮ› + ๐‘ โ†’๐‘โข๐พ 0 ๐‘†โข ๐œ‹ 0 at Belle

We report a precise measurement of the ratio of branching fractions โ„ฌโก(ฮ›$^+_๐‘$ โ†’ ๐‘โข๐พ$^0_๐‘†$โข๐œ‹ 0 )/โ„ฌโก(ฮ›$^+_๐‘$ โ†’ ๐‘โข๐พ โˆ’ โข๐œ‹ + ) using 980 fb โˆ’1 of ๐‘’ + โข๐‘’ โˆ’ data from the Belle experiment. We obtain a value of โ„ฌโก(ฮ›$^+_๐‘$ โ†’ ๐‘โข๐พ$^0_๐‘†$โข๐œ‹ 0 )/โ„ฌโก(ฮ›$^+_๐‘$ โ†’ ๐‘โข๐พ โˆ’ โข๐œ‹ + ) =0.339 ยฑ0.002 ยฑ0.009, where the first and second uncertainties are statistical and systematic, respectively. This Belle result is consistent with the previous measurement from the CLEO experiment but has a fivefold improvement in precision. By combining our result with the world average โ„ฌโก(ฮ›$^+_๐‘$ โ†’ ๐‘โข๐พ โˆ’ โข๐œ‹ + ), we obtain the absolute branching fraction โ„ฌโก(ฮ›$^+_๐‘$ โ†’ ๐‘โข๐พ$^0_๐‘†$โข๐œ‹ 0 ) =(2.12 ยฑ 0.01 ยฑ0.05 ยฑ0.10)%, where the uncertainties are statistical, systematic, and the uncertainty in the absolute branching fraction scale โ„ฌโก(ฮ›$^+_๐‘$ โ†’ ๐‘โข๐พ โˆ’ โข๐œ‹ + ), respectively. This measurement can shed light on hadronic decay mechanisms in charmed baryon decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSโ†—
DOE OSTI2025

Measurement of branching fractions, C P asymmetry, and isospin asymmetry for B โ†’ ฯ ฮณ decays using Belle and Belle II data

We present measurements of B + โ†’ ฯ + ฮณ and B 0 โ†’ ฯ 0 ฮณ decays using a combined data sample of 772 ร— 10 6 B B ยฏ pairs collected by the Belle experiment and 387 ร— 10 6 B B ยฏ pairs collected by the Belle II experiment in e + e โˆ’ collisions at the ฯ’ ( 4 S ) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II datasets yields 114 ยฑ 12 B + โ†’ ฯ + ฮณ and 99 ยฑ 12 B 0 โ†’ ฯ 0 ฮณ decays. The measured branching fractions are ( 13.1 โˆ’ 1.9 โˆ’ 1.2 + 2.0 + 1.3 ) ร— 10 โˆ’ 7 and ( 7.6 ยฑ 1.3 โˆ’ 0.8 + 1.0 ) ร— 10 โˆ’ 7 for B + โ†’ ฯ + ฮณ and B 0 โ†’ ฯ 0 ฮณ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry A I ( B โ†’ ฯ ฮณ ) = ( 10.9 โˆ’ 11.7 โˆ’ 7.3 + 11.2 + 7.8 ) % and the direct C P asymmetry A C P ( B + โ†’ ฯ + ฮณ ) = ( โˆ’ 8.2 ยฑ 15.2 โˆ’ 1.3 + 2.0 ) % . Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)โ†—
DOE OSTI2025

Observation of time-dependent C P violation and measurement of the branching fraction of B 0 โ†’ J / ฯˆ ฯ€ 0 decays

We present a measurement of the branching fraction and time-dependent charge-parity ( C P ) decay-rate asymmetries in B 0 โ†’ J / ฯˆ ฯ€ 0 decays. The data sample was collected with the Belle II detector at the SuperKEKB asymmetric e + e โˆ’ collider in 2019โ€“2022 and contains ( 387 ยฑ 6 ) ร— 10 6 B B ยฏ meson pairs from ฯ’ ( 4 S ) decays. We reconstruct 392 ยฑ 24 signal decays and fit the C P parameters from the distribution of the proper-decay-time difference of the two B mesons. We measure the branching fraction to be ( B 0 โ†’ J / ฯˆ ฯ€ 0 ) = ( 2.00 ยฑ 0.12 ยฑ 0.09 ) ร— 10 โˆ’ 5 and the direct and mixing-induced C P asymmetries to be C C P = 0.13 ยฑ 0.12 ยฑ 0.03 and S C P = โˆ’ 0.88 ยฑ 0.17 ยฑ 0.03 , respectively, where the first uncertainties are statistical and the second are systematic. We observe mixing-induced C P violation with a significance of 5.0 standard deviations for the first time in this mode. Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)โ†—
DOE OSTI2024

Evidence of h b ( 2 P ) โ†’ ฯ’ ( 1 S ) ฮท Decay and Search for h b ( 1 P , 2 P ) โ†’ ฯ’ ( 1 S ) ฯ€ 0 with the Belle Detector

We report the first evidence for the h b ( 2 P ) โ†’ ฯ’ ( 1 S ) ฮท transition with a significance of 3.5 standard deviations. The decay branching fraction is measured to be B [ h b ( 2 P ) โ†’ ฯ’ ( 1 S ) ฮท ] = ( 7.1 โˆ’ 3.2 + 3.7 ยฑ 0.8 ) ร— 10 โˆ’ 3 , which is noticeably smaller than expected. We also set upper limits on ฯ€ 0 transitions of B [ h b ( 2 P ) โ†’ ฯ’ ( 1 S ) ฯ€ 0 ] < 1.8 ร— 10 โˆ’ 3 , and B [ h b ( 1 P ) โ†’ ฯ’ ( 1 S ) ฯ€ 0 ] < 1.8 ร— 10 โˆ’ 3 , at the 90% confidence level. These results are obtained with a 131.4 fb โˆ’ 1 data sample collected near the ฯ’ ( 5 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e โˆ’ collider. Published by the American Physical Society 2024

Kovalenko, E. (ORCID:0000000180841931)โ†—
DOE OSTI2024

Measurement of the e + e โˆ’ โ†’ ฯ€ + ฯ€ โˆ’ ฯ€ 0 cross section in the energy range 0.62โ€“3.50 GeV at Belle II

We report a measurement of the e + e โˆ’ โ†’ ฯ€ + ฯ€ โˆ’ ฯ€ 0 cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an e + e โˆ’ data sample corresponding to 191 fb โˆ’ 1 of integrated luminosity, collected at a center-of-mass energy at or near the ฯ’ ( 4 S ) resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extracted by fitting the two-photon mass distribution in e + e โˆ’ โ†’ ฯ€ + ฯ€ โˆ’ ฯ€ 0 ฮณ events, which involve a ฯ€ 0 โ†’ ฮณ ฮณ decay and an energetic photon radiated from the initial state. Signal efficiency corrections with an accuracy of 1.6% are obtained from several control data samples. The uncertainty on the cross section at the ฯ‰ and ฯ• resonances is dominated by the systematic uncertainty of 2.2%. The resulting cross sections in the 0.62โ€“1.80 GeV energy range yield a ฮผ 3 ฯ€ = [ 48.91 ยฑ 0.23 ( stat ) ยฑ 1.07 ( syst ) ] ร— 10 โˆ’ 10 for the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. This result differs by 2.5 standard deviations from the most precise current determination. Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)โ†—
DOE OSTI2024

Search for the baryon number and lepton number violating decays ฯ„ โˆ’ โ†’ ฮ› ฯ€ โˆ’ and ฯ„ โˆ’ โ†’ ฮ› ยฏ ฯ€ โˆ’ at Belle II

We present a search for the baryon number B and lepton number L violating decays ฯ„ โˆ’ โ†’ ฮ› ฯ€ โˆ’ and ฯ„ โˆ’ โ†’ ฮ› ยฏ ฯ€ โˆ’ produced from the e + e โˆ’ โ†’ ฯ„ + ฯ„ โˆ’ process, using a 364 fb โˆ’ 1 data sample collected by the Belle II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have | ฮ” ( B โˆ’ L ) | equal to 2 and 0, respectively. Upper limits at 90% credibility level on the branching fractions of ฯ„ โˆ’ โ†’ ฮ› ฯ€ โˆ’ and ฯ„ โˆ’ โ†’ ฮ› ยฏ ฯ€ โˆ’ are determined to be 4.7 ร— 10 โˆ’ 8 and 4.3 ร— 10 โˆ’ 8 , respectively. Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)โ†—