diff --git a/.constraints/py3.7.txt b/.constraints/py3.7.txt
deleted file mode 100644
index 89b5c780..00000000
--- a/.constraints/py3.7.txt
+++ /dev/null
@@ -1,236 +0,0 @@
-#
-# This file is autogenerated by pip-compile with Python 3.7
-# by the following command:
-#
-#    pip-compile --extra=dev --no-annotate --output-file=.constraints/py3.7.txt --resolver=backtracking --strip-extras --unsafe-package=ampform-dpd --unsafe-package=pip --unsafe-package=setuptools
-#
-absl-py==2.0.0
-accessible-pygments==0.0.4
-aiofiles==22.1.0
-aiosqlite==0.19.0
-alabaster==0.7.13
-ampform==0.14.6
-anyio==3.7.1
-argon2-cffi==23.1.0
-argon2-cffi-bindings==21.2.0
-arrow==1.2.3
-astunparse==1.6.3
-attrs==23.1.0
-babel==2.13.0
-backcall==0.2.0
-beautifulsoup4==4.12.2
-black==23.3.0
-bleach==6.0.0
-cached-property==1.5.2
-cachetools==5.3.1
-certifi==2023.7.22
-cffi==1.15.1
-cfgv==3.3.1
-chardet==5.2.0
-charset-normalizer==3.3.0
-click==8.1.7
-cloudpickle==2.2.1
-colorama==0.4.6
-comm==0.1.4
-coverage==7.2.7
-cycler==0.11.0
-debugpy==1.7.0
-decorator==5.1.1
-defusedxml==0.7.1
-deprecated==1.2.14
-distlib==0.3.7
-dm-tree==0.1.8
-docstring-to-markdown==0.12
-docutils==0.17.1
-entrypoints==0.4
-exceptiongroup==1.1.3
-execnet==2.0.2
-fastjsonschema==2.18.1
-filelock==3.12.2
-flatbuffers==23.5.26
-fonttools==4.38.0
-fqdn==1.5.1
-gast==0.4.0
-google-auth==2.23.2
-google-auth-oauthlib==0.4.6
-google-pasta==0.2.0
-graphviz==0.20.1
-greenlet==3.0.0
-grpcio==1.59.0
-h5py==3.8.0
-hepunits==2.3.2
-identify==2.5.24
-idna==3.4
-imagesize==1.4.1
-iminuit==2.18.0
-importlib-metadata==6.7.0
-importlib-resources==5.12.0
-iniconfig==2.0.0
-ipykernel==6.16.2
-ipympl==0.9.3
-ipython==7.34.0
-ipython-genutils==0.2.0
-ipywidgets==8.1.1
-isoduration==20.11.0
-jax==0.3.25
-jaxlib==0.3.25
-jedi==0.18.2
-jinja2==3.1.2
-json5==0.9.14
-jsonpointer==2.4
-jsonschema==4.17.3
-jupyter-cache==0.5.0
-jupyter-client==7.4.9
-jupyter-core==4.12.0
-jupyter-events==0.6.3
-jupyter-lsp==1.5.1
-jupyter-server==1.24.0
-jupyter-server-fileid==0.9.0
-jupyter-server-ydoc==0.8.0
-jupyter-ydoc==0.2.4
-jupyterlab==3.6.6
-jupyterlab-code-formatter==2.2.1
-jupyterlab-lsp==3.10.2
-jupyterlab-myst==1.2.0
-jupyterlab-pygments==0.2.2
-jupyterlab-server==2.24.0
-jupyterlab-widgets==3.0.9
-keras==2.11.0
-kiwisolver==1.4.5
-latexcodec==2.0.1
-libclang==16.0.6
-livereload==2.6.3
-markdown==3.4.4
-markdown-it-py==2.2.0
-markupsafe==2.1.3
-matplotlib==3.5.3
-matplotlib-inline==0.1.6
-mdit-py-plugins==0.3.5
-mdurl==0.1.2
-mistune==3.0.2
-mpmath==1.3.0
-mypy-extensions==1.0.0
-myst-nb==0.17.2
-myst-parser==0.18.1
-nbclassic==1.0.0
-nbclient==0.5.13
-nbconvert==7.6.0
-nbformat==5.8.0
-nbmake==1.2.1
-nest-asyncio==1.5.8
-nodeenv==1.8.0
-notebook==6.5.6
-notebook-shim==0.2.3
-numpy==1.21.6
-oauthlib==3.2.2
-opt-einsum==3.3.0
-packaging==23.2
-pandocfilters==1.5.0
-parso==0.8.3
-particle==0.23.0
-pathspec==0.11.2
-pexpect==4.8.0
-phasespace==1.9.0
-pickleshare==0.7.5
-pillow==9.5.0
-pkgutil-resolve-name==1.3.10
-platformdirs==3.11.0
-pluggy==1.2.0
-pre-commit==2.21.0
-prometheus-client==0.17.1
-prompt-toolkit==3.0.39
-protobuf==3.19.6
-psutil==5.9.5
-ptyprocess==0.7.0
-pyasn1==0.5.0
-pyasn1-modules==0.3.0
-pybtex==0.24.0
-pybtex-docutils==1.0.3
-pycparser==2.21
-pydantic==1.10.13
-pydata-sphinx-theme==0.13.3
-pygments==2.16.1
-pyparsing==3.1.1
-pyproject-api==1.5.3
-pyrsistent==0.19.3
-pytest==7.4.2
-pytest-cov==4.1.0
-pytest-xdist==3.3.1
-python-constraint==1.4.0
-python-dateutil==2.8.2
-python-json-logger==2.0.7
-python-lsp-jsonrpc==1.0.0
-python-lsp-server==1.7.4
-pytoolconfig==1.2.5
-pytz==2023.3.post1
-pyyaml==6.0.1
-pyzmq==24.0.1
-qrules==0.9.8
-requests==2.31.0
-requests-oauthlib==1.3.1
-rfc3339-validator==0.1.4
-rfc3986-validator==0.1.1
-rope==1.9.0
-rsa==4.9
-ruff==0.0.292
-scipy==1.7.3
-send2trash==1.8.2
-singledispatchmethod==1.0
-six==1.16.0
-sniffio==1.3.0
-snowballstemmer==2.2.0
-soupsieve==2.4.1
-sphinx==5.3.0
-sphinx-autobuild==2021.3.14
-sphinx-book-theme==1.0.1
-sphinx-codeautolink==0.15.0
-sphinx-copybutton==0.5.2
-sphinx-design==0.4.1
-sphinx-togglebutton==0.3.2
-sphinxcontrib-applehelp==1.0.2
-sphinxcontrib-bibtex==2.6.1
-sphinxcontrib-devhelp==1.0.2
-sphinxcontrib-htmlhelp==2.0.0
-sphinxcontrib-jsmath==1.0.1
-sphinxcontrib-qthelp==1.0.3
-sphinxcontrib-serializinghtml==1.1.5
-sqlalchemy==1.4.49
-sympy==1.10.1
-tabulate==0.9.0
-tensorboard==2.11.2
-tensorboard-data-server==0.6.1
-tensorboard-plugin-wit==1.8.1
-tensorflow==2.11.0
-tensorflow-estimator==2.11.0
-tensorflow-io-gcs-filesystem==0.34.0
-tensorflow-probability==0.19.0
-tensorwaves==0.4.10
-termcolor==2.3.0
-terminado==0.17.1
-tinycss2==1.2.1
-tomli==2.0.1
-tornado==6.2
-tox==4.8.0
-tqdm==4.66.1
-traitlets==5.9.0
-typed-ast==1.5.5
-typing-extensions==4.7.1 ; python_version < "3.8.0"
-ujson==5.7.0
-uri-template==1.3.0
-urllib3==2.0.6
-virtualenv==20.24.5
-wcwidth==0.2.8
-webcolors==1.13
-webencodings==0.5.1
-websocket-client==1.6.1
-werkzeug==2.2.3
-wheel==0.41.2
-widgetsnbextension==4.0.9
-wrapt==1.15.0
-y-py==0.5.9
-ypy-websocket==0.8.2
-zipp==3.15.0
-
-# The following packages are considered to be unsafe in a requirements file:
-# ampform-dpd
-# setuptools
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c2f20dfd..ed1f648c 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -43,7 +43,7 @@ repos:
     hooks:
       - id: nbqa-pyupgrade
         args:
-          - --py37-plus
+          - --py38-plus
       - id: nbqa-ruff
         args:
           - --fix
@@ -112,7 +112,7 @@ repos:
     hooks:
       - id: pyupgrade
         args:
-          - --py37-plus
+          - --py38-plus
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
     rev: v0.0.292
diff --git a/docs/conf.py b/docs/conf.py
index 05ec2219..92950fc0 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -1,22 +1,17 @@
 from __future__ import annotations
 
+import contextlib
 import os
 import shutil
 import subprocess
 import sys
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as get_package_version
 
 import requests
 from pybtex.plugin import register_plugin
 
-if sys.version_info < (3, 8):
-    from importlib_metadata import PackageNotFoundError
-    from importlib_metadata import version as get_package_version
-else:
-    from importlib.metadata import PackageNotFoundError
-    from importlib.metadata import version as get_package_version
-
 sys.path.insert(0, os.path.abspath("."))
-import contextlib
 
 from _relink_references import relink_references
 from _unsrt_et_al import MyStyle
diff --git a/pyproject.toml b/pyproject.toml
index 948a5cd0..27730912 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -17,7 +17,6 @@ classifiers = [
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
-    "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python",
@@ -31,13 +30,12 @@ dependencies = [
     "cloudpickle",
     "sympy >=1.10", # module sympy.printing.numpy and array expressions with shape kwarg
     "tensorwaves[jax]",
-    'typing-extensions; python_version <"3.8.0"',
 ]
 description = "Symbolic expressions for Dalitz-Plot Decomposition"
 dynamic = ["version"]
 license = {text = "GPLv3 or later"}
 name = "ampform-dpd"
-requires-python = ">=3.7"
+requires-python = ">=3.8"
 
 [project.optional-dependencies]
 dev = [
@@ -62,7 +60,6 @@ doc = [
     "sphinxcontrib-bibtex",
     "tensorwaves[phsp]",
     "tqdm",
-    'importlib-metadata; python_version <"3.8.0"',
 ]
 format = [
     "black",
@@ -77,7 +74,6 @@ jupyter = [
     "jupyterlab-lsp",
     "jupyterlab-myst",
     "python-lsp-server[rope]",
-    'ypy-websocket <0.8.3; python_version <"3.8.0"',
 ]
 lint = [
     "ruff",
@@ -103,7 +99,6 @@ test = [
     "pytest >=6.0", # pyproject.toml
     "pytest-cov",
     "pytest-xdist",
-    'nbmake <1.3; python_version <"3.8.0"',
 ]
 tf = [
     "tensorwaves[tf]",
@@ -152,7 +147,6 @@ preview = true
 target-version = [
     "py310",
     "py311",
-    "py37",
     "py38",
     "py39",
 ]
@@ -253,7 +247,7 @@ extend-select = [
     "YTT",
 ]
 ignore = [
-    "B028", # missing explicit stacklevel keyword
+    "B028",
     "C408",
     "D101",
     "D102",
@@ -266,7 +260,7 @@ ignore = [
     "D416",
     "E501",
     "ISC003",
-    "PLR0913", # sympy class
+    "PLR0913",
     "S301",
     "SIM108",
 ]
@@ -275,7 +269,7 @@ src = [
     "src",
     "tests",
 ]
-target-version = "py37"
+target-version = "py38"
 task-tags = ["cspell"]
 
 [tool.ruff.pep8-naming]
diff --git a/src/ampform_dpd/__init__.py b/src/ampform_dpd/__init__.py
index a373afc1..dc13fe91 100644
--- a/src/ampform_dpd/__init__.py
+++ b/src/ampform_dpd/__init__.py
@@ -1,9 +1,9 @@
 # cspell:ignore msigma
 from __future__ import annotations
 
-import sys
 from functools import lru_cache
 from itertools import product
+from typing import Literal, Protocol
 
 import sympy as sp
 from ampform.sympy import PoolSum
@@ -13,6 +13,7 @@
 from sympy.physics.quantum.spin import CG, WignerD
 from sympy.physics.quantum.spin import Rotation as Wigner
 
+from ampform_dpd.angles import formulate_scattering_angle, formulate_zeta_angle
 from ampform_dpd.decay import (
     IsobarNode,
     LSCoupling,
@@ -23,13 +24,6 @@
 )
 from ampform_dpd.spin import create_spin_range
 
-from .angles import formulate_scattering_angle, formulate_zeta_angle
-
-if sys.version_info < (3, 8):
-    from typing_extensions import Literal, Protocol
-else:
-    from typing import Literal, Protocol
-
 
 @frozen
 class AmplitudeModel:
diff --git a/src/ampform_dpd/decay.py b/src/ampform_dpd/decay.py
index 93e17e13..417451d2 100644
--- a/src/ampform_dpd/decay.py
+++ b/src/ampform_dpd/decay.py
@@ -1,8 +1,7 @@
 """Data structures that describe a three-body decay."""
 from __future__ import annotations
 
-import sys
-from typing import TYPE_CHECKING, Dict
+from typing import TYPE_CHECKING, Dict, Literal
 
 from attrs import field, frozen
 from attrs.validators import instance_of
@@ -12,11 +11,6 @@
 if TYPE_CHECKING:
     import sympy as sp
 
-if sys.version_info < (3, 8):
-    from typing_extensions import Literal
-else:
-    from typing import Literal
-
 
 @frozen
 class Particle: